Prepared For:

Minnesota Association of Metal Finishers 7630 b o x Avenue South

Richfield, MN 55423

Prepared By:

Capsule Environmental Engineering, Inc. 1970 Oakcrest Avenue

St. Paul, MN 55113 (612) 636-2644

In Conjunction With:

The Minnesota Technical Assistance Program (MnTAP) 1313 5th Street SE Suite 207

Minneapolis, MN 55414 (612) 627-4646

Funded in Part By:

The Minnesota Office of Waste Management 1350 Energy Lane

St. Paul, MN 55108 (612) 649-5750

July 1993

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NOTE

This manual was prepared by Capsule Environmental Engineering Inc., in conjunction with the Minnesota Association of Metal F i i e r s and the Minnesota Technical Assistance Program. F+mding for this project was prod4 in part by the Minnesota Office of Waste Management. Capsule Envitoarmentsl Engineerins does not warrant the effectiveness of the processes described for any general or specific purpose.

INTRODUCTION

This manual is intended to assist the metal finishing industry in idenbfyng, assessing, and implementing pollution prevention options. A wide variety of physical, chemical, and electrochemical processes are used in the metal finishing industry. Various waste streams are generated, including spent plating baths, spent process baths, rinse water, solvents, air emissions, and misceheous solid waste. The reduction of waste generation at the source benefits the indw by reducing waste disposal costs, reducing raw material costs, increasing worker safety, and lowering the liabilities assodated with waste disposal.

The contents of this manual include:

Section I.

Section II.

'Section m. Section lV.

Section V.

Section VI. Section VII.

Pollution prevention regulation overview, pollution prevention assessment, and pollution prevention phns

Electroplating waste source reduction and recovery, and pretreatment alternatives

Painting waste source reduction opportunities

Degreasing waste source reduction and recovery, and treatment alternatives

Metal pretreatment, source reduction and recovery, and treatment alternatives

Machining waste source reduction and recovery, and treatment alternatives

Water conservation and rinsing fundamentals for electroplaters

Section VIII. Vendor lists

TABLE OF CONTENTS

I

Section 1 . Pollution Prevention .................................... 1 A . Regulatory Initiatives ...................................... 2

1 . FederalEfforts ........................................ 2 2 . Minnesota and Other State Worts .......................... 2

B . The Pollution Prevention Assessment ........................... 4 1 . Introduction .......................................... 4 2 . Case Stidy: XYZ Equipment Company ....................... 4 3 . Gettlng Started ....................................... 5 4 . Keyhdivid ual ........................................ 6 5 . Upper Management Support .............................. 6 6 . Project TeamBuilding ................................... 7 7 . The Assessment ....................................... 7 8 . Cleaning ............................................ 8

3 . Industry Initiatives .................................... 3

9 . Painting ............................................ 9 10 . Plating ............................................ 10 11 . Iden-g Options ................................... 12 12 . Evaluating Options .................................... 14 13 .. Technical Evaluation ................................... 14 14 . Economic Evaluation ................................... 16 15 . PrioritizingOptions ................................... 17

C . Preparing a Pollution Prevention Plan .......................... 19 2 . Description of the Genera- Processes ..................... 19 3 . Description of Current and Past Practices ..................... 20 4 . Investigation of Options ................................ 20 5 . Feasibility .......................................... 21 6 . Development of Goals .................................. 21 7 . Measurement of Progress ............................... 21 8 . Annual Progress Reports ................................ 22

D . Pollution Prevention Bibliography ............................. 22

1 . Policy statement ...................................... 19

Section 11 . Electroplating ........................................ 24 A . Source Reduction ........................................ 25

1 . Drag-out Reduction ................................... 25 2 . Chemical Process Control ............................... 26 3 . Bath Purification ...................................... 26 4 . Alkaline Cleaners ..................................... 30 5 . Cyanide Process Bath Alternatives ......................... 30 6 . Zinc and Cadmium Process Alternatives ..................... 32 7 . Hexavalent Chromium Process Bath Altematiws ............... 34

B . Recovery and Treatment Alternatives .......................... 34 1 . Precipitation ........................................ 34 2 . IonExchange ........................................ 35 3 . Electrolytic Metal Recovery .............................. 36 4 . Evaporation ......................................... 37 5 . Electrodialysis ....................................... 37 6 . Reverse Osmosis ..................................... 38

7 . Ultrafiltration ........................................ 38 8 . Microfiltration ....................................... 38 9 . Closed Loop Systems .................................. 38

Section III . Painting ........................................... 40 A . Source Reduction ........................................ 41

1 . Application Equipment ................................. 41 2 . Alternative Coatings ................................... 42 3 . Equipment Cleaning and Stripping Alternatives ................ 44 4 . Solvent Use Reduction Measures .......................... 45 5 . Segregation ......................................... 46 6 . Process Alternatives ................................... 46 7 . Treatment and Recovery Alternatives ....................... 47

B . Painting Bibliography ..................................... 48 Section IV . Degreasing ......................................... 49

A. Source Reduction ........................................ 50 2 . Considerations in Cleaner Selection ........................ 53

B . Recovery and Treatment Alternatives .......................... 54 1 . Cleaner Solution and Rinsewater Recycling ................... 54

1 . Degreasing Alternatives ................................. 50

C . Degreasing Bibliography ................................... 55 Section V . Metal Pretreatment .................................... 56

A . Source Reduction ........................................ 57 B . Recovery and Treatment Alternatives .......................... 58 1 . Pretreatment Process ................................... 57 ! C . Metal Pretreatment Bibliography .............................. 59

SectionVI . Machining .......................................... 60 A . Source Reduction ........................................ 61

1 . Coolant Selection ..................................... 61 2 . Coolant Consolidation .................................. 62 3 . Optimization of Operating Parameters ....................... 62 4 . Housekeeping ....................................... 62

B . Recovery and Treatment Alternatives .......................... 62 1 . Coolant Treatment .................................... 62

C . Machinrng Bibliography .................................... 63 2 . Coolant Recycling ..................................... 63

Section VII . Water Conservation and Rinsing for Electxoplaters .............. 64 A . Introduction ........................................... 65 B . Part One: Water Conservation ............................... 65

1 . Baseline Measurement .................................. 65 2 . Good Housekeeping ................................... 66 3 . Flow Rate Reduction ................................... 66

C . Part Two: Rinsing Fundamentals ............................. 67 1 . ThePurpose ofRinsing ................................. 67 2 . OptimizingtheRinsing Process ........................... 68 3 . Determination of Present Operating Conditions ................ 69 4 . Drag-out Measurement ................................. 69 5 . J.(inse Water Flow.Rate ................................. 70

6 . Total Water Usage .................................... D . Part Three: Options for Improvement ..........................

2 . Drag-out Reduction ................................... 3 . Rinsing Techmpes ................................... 4 . Integration of Options ..................................

1 . WaterQuality .......................................

E . Water Conservation and Rinsing for Electroplaters Bibliography ........ Section VIII . Lists of Vendors ......................................

AnodeBags ............................................... Barrels for Plating Lines ...................................... Chemicals for Plating ........................................ Chemicals for Blackening ...................................... Chemicals for Precious Metal Plating .............................. Chemicals for Testing Solutions .................................

Chillers For Plating Baths ..................................... . Danglers .................................................

Chemicals for Phosphating ....................................

ChemicalDestrudSystems .................................... W e r s ................................................. Corrosioncabinets .......................................... Evaporators ............................................... FiltrationSyste ms ........................................... Filters ................................................... Filter Presses .............................................. Immersion HeaterdCoils ...................................... Heaters for Plating Solutions ................................... Installation of Plating Systems .................................. Ion - Exchange Systems ......................................

Nickel Recovery ............................................. Plating Lines (Rebuilt) ........................................ Pumps .................................................. Racks for P lahg Lines ....................................... Recovery Systems ...........................................

Scrubbers ( A i r Poilution Equipment) .............................. SpinOryers ...............................................

Thickness Testers for Plating ...................................

Metals .................................................. Mixers .................................................. Plating Lines (Automatic) .....................................

Recfif5ers ................................................. Rinse Water Controllers ...................................... SludgeDxyers ............................................. Tanks ................................................... TanlcLiners ............................................... TitaniumProducts .......................................... LocalDistributors ...........................................

70

70 n 74 78 79

70

81 82 82 83 84 84 84 84 85 85 85 85 86 86 86 87 87 87 a8 88 88 89 89 89 89 89 90 90 90 91 91 91 91 92 92 92 92 93 93

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A. REGULATORY INITIATIVES

Presented below is a brief overview of federal and state pollution prevention initiatives, and nonregulatory actions focusing on pollution prevention.

1 1, Federal Efforts The federal government truly began to focus on pollution prevention with the initiation of the Pollution Prevention Act (FPA) of 1990 and its extension into Title Dl of the Superfund Amendments and Reauthorization Act (SARA). Under the PPA, Congress declared that pollution should be prevented or reduced in an environmentally safe manner; pollution that cannot be prevented or recycled should be treated, again, in an environmentally safe m e r . The PPA states that dsposal or other release into the environment should be employed only as a last resort.

As mentioned above, an extension of the PPA is the mandatory reporting of source reduction and recycling activities under SARA Title III, Section 313. This section, better known as Form R reporhg, now requires those facilities in the SIC codes 20 through 39 with ten or more full-time employees to annually report their pollution prevention activities for approximately 320 toxic chemicals and compounds to the EPA

Two additional pollution prevention initiatives at the federal level involve ozone- depleting chemicals and the general storm water discharge permit program. The amendments on drloroflurocarbons (CFG) ban their production, as well as any unsafe substitutes which deplete the ozone layer, by December 31,1995. EPA's current proposal for general storm water discharge permits require a stormwater pollution prevention plan for each fa&fy subject to this type of permit.

2. Minnesota and Other State Efforts

Individual states have taken a more active role in addressing pollution prevention. Several states have enacted bold or innovative legislation, which in some cases has been adopted by other states or the federal government. The most common features of these laws are provisions for financial, technical, or e d u c a t i d assistance, imposition of fees or taxes on hazardous waste generators, establishment of spe& reduction goals, encouragement of voluntary pollution prevention actions, and prohibition of the use of certain compounds.

Several states include reduction goals in their legislation to promote pollution prevention. To date, eight states have established numeric reduction goals. These goals mainly target the generation of hazardous waste though some m y include toxic air emissions or the use or release of toxic chemicals. The numeric goals also vary, but a general range is 25 percent to 50 percent reduction within 10 years.

States have shown the greatest creativity and innovation in the methods they've established for encouraging industry to voluntarily prevent pollution. Most are promoting pollution prevention through economic andor regulatory incentives. These incentives range from publicly recognizing corporate pollution prevention actions with monetary awards to setting up fee systems or regulatory incentives to encourage pollution prevention. Some states are also giving special waivers to facilities that choose to invest in pollution prevention technolops with greater environmental benefits than those resulting from n o d compliance.

Beyond the enactment of general pollution prevention legislatian, the other sgni6cant initiative at the state level is the necessity for pollution prevention or to* use redudion plans, now requited in 17 states. Each state's plan requirements vary, but common elements include the following: a description of wastes and emissions; current pollution prevention practices, and identification and evaluation of options; pollution prevention goals; employee training; and an implementation schedule.

In Minnesota, all fadities filing Toxic Release Inventory Reporting forms (Fm Rs) under Title III, Section 313 of the federal Superfund Amendments and Reauthorization Act (SARA) must prepare a pollution prevention plan. The plan includes strategies and goals for the reduction or complete elimination of pollutants for a three year period. .Annual progress reports must be filed with the state that detail progress toward the pollution prevention goals in the plan. The plan must be updated every two years. Additional infomation regarding Minnesota pollution prevention planning can be found in Section C, 'Preparing a Pollution Prevention Plan.'

3. Industry Initiatives

The metal finishing industxy in Minnesota is active in promoting pollution prevention among its constituents. In 1982, a cooperative effort between the Metropolitan Recovery Corporation (a company made up of over 20 metal bshing firms known as h4RC), Lancy Recovery Inc., and the State of Minnesota resulted in the construction of a central treatment and recovery facility. This facility, Metro Recovery Systems (MRS), served to allow cost-effective waste treatment and recovery for the metal finishing industry. In 1992, MRS (including the share owned by MRC) was purchased by U.S. Filter, Inc.

4. Nonregulatoxy Initiatives

The final examination of polhrtion prevention deals with the highly influential nonregulatory activities. One major initiative is EPA's Industxial Toxics Project, more commonly d e d the 3/50 program. This program invites the largest dischargers of 17 priority pollutants to voluntarily reduce their releases or off-site transfers. The goals of the program are a 33 percent reduction by 1992 and a 50 percent reduction by 1995 in releases from these priority chemicals, using 1988 Fonn R releases as a basis. The Minnesota equivalent of this program is called the Minnesota-50 Program.

Other activities influencing pollution prevention are those by trade associations. Groups such as the Minnesota Association of Metal Finishers, Chemical Manufacturers Assodation, American Petroleum Institute, and the National Paint and Coatings Assodation have established formal programs that require their members to reduce

The last of the nonregulatory activities are those conducted by atizens. Citizens have been able to force industry to conduct pollution prevention activities by including provisions in suits against fadlities that do not comply with release reporting requirements, or by demanding 'green' products that are made using environmentaUy safe processes or chemicals.

In s ~ m m u y , regulatory and nonregulatory efforts are being made to encourage industry to reduce pollution at the source rather than treating it at the end of the pipe. While mandated pollution prevention requirements continue to increase, it is the voluntary efforts that will put industrial facilities ahead of the pack when it comes to regulatory . compliance. Such efforts may include changing to less polluting processes or raw materials, controlling inventory, improving housekeeping and management practices, and inueasing process efficiency. These activities will not only help industxy reduce its detrimental effect on the environment and ensure its regulatory compliance, but they will also provide an economic advantage by reducing disposal costs and the associated liability.

B. THE POLLUTION PREVENTION ASSESSMENT I. Introduction

Pollution prevention plans must address how a company will work towards reducing the pollution from the plant by modifying the manufactwing processes and operations rather than through mure traditional end-of-pipe treatment methods. In addition to process changes, pollution prevention goals can also be obtained through product redesign, inventory control measures, and proper training.

Pollution prevention, when viewed as a typical engineering project, is not magic or especially unique. The techtllques and procedures presented in this paper are similar to those used when a firm develops a plan to reduce the manufactured cost of a product or improve product quality. The key pollution prevention issues of establishing goals, obtaining management support, developing a leader, selecting a project team, communicating with personnel and assessing operations are the same issues faced in other projects. The only difference is that in these assessments, efforts focus on the pollution generated from the manufacturing processes and operations in addition to product quality and manufactured cost.

The initial step to be taken in developing a pollution prevention plan is the waste reduction assessment. A generic hypothetical manufacturing facility is used as a case study to help explain the pzinaples presented.

2. Case Study: XYZ Equipment Company

The hypothetical facility used as a case study for our pollution prevention project is called XYZ Equipment Company, with headquarters and manufacturing facilities in Bora

Bora, Minnesota. The facility manufactures a cabinet which contains various small machined parts. The cabinet is made of sheet metal and is painted for both aesthetics and corrosion protection. The i n t e d parts are carbon steel and are zinc plated with a chromate conversion coating to protect them from corrosion.

The XYZ plant is a simple operation. Parts are machined and cabinets formed off site and shipped to XYZ weekly. When received, parts are stored until they are needed. Parts are covered with a rust-preventative oil coating at XYZ's supplier to prevent corrosion during storage.

As needed, parts are removed from storage and taken to the plant's vapor d-easing cleaning system to remove oil and shop dust. Trichloroethylene (TCE) boils in a sump in the bottom of the degreaser and the fumes rise to a vapor zone. When a cold part is placed in the hot vapor zone, the TCE condenses on the part, removing the 'soils.' The TCE then chips back into the sump. Cooling coils filled with flowing water maintain a cold zone above the sump through which the heavier-thana solvent should not escape. Small parts are placed in a basket and hung in the degreaser using a hoist. Panels for cabinets are also supported using the hoist. To reduce employee exposure to

I the chlorinated solvent, a lip vent was installed on the degreaser to remove the fumes. After the parts are cleaned, cabinets are assembled and painted, and internal parts are zinc plated.

Painting is done using a conventional manual high-pressure spray system which is used to apply the one color of solvent-based paint used on the cabinets. The one painting booth has dry filters to catch paint overspray.

Xnternal parts are zinc plated from a dnctyanide plating bath. Parts are placed into barrelsandmanuallycaniedthroughthebathsontheline. Bathsindudean electrocleaning tank which is followed by two rinses, an arid adivation tank followed by two rinses, the zinc bath followed by two rinses, a chromate tank, a hot rinse and a d q h g stage.

Rinsewater and bath dumps are piped to a wastewater treatment area. Separate lines are used for cyanidwontaining, duome-containing and general wastewaters. Wastewaters containing cyanides are treated with sodium hypochlorite to oxidize the cyanides. Hexavalent chrome is reduced to the less toxic trivalent form using sodium bisulfite. Au. wastewaters are then dined and the pH of the solution increased to precipitate out the metals. The &an water passes hgh a clarifier before being discharged and the sludge is sent to a filter pres.

3. Getting Started

Some of the major considerations in developing a successful pollution prevention program are to idenbfy one key person to lead the project, to develop upper management support for the work that will be required and to build a redts-oriented project team.

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4. Key Individual

A key individual is needed to lead the project. This person should have the following characteristics:

General knowledge of the plant processes Ability to work with and lead other team members Strong communication skills Commitment to the project Good listening skills An open mind

Notice that this person does not necessarily need to know environmental regulations or be a technical specialist on the plant processes. These skills are all readily available either in other plant personnel or through outside resources. Through the course of this project, this individual will develop a strong understanding of all plant processes and options for future improvements. In that sense, the pollution prevention efforts can be a grooming process for developing an individual’s manufacturing management skills. The last two items mentioned are good listening skills and an open mind. A successful pollution prevention leader should not have preconceived notions of what would be the best way to modify certain processes. The person needs to be able to solicit and listen to the ideas of machine operators, product designers and maintenance personnel who will be most familiar with the particular operation.

This person must be given the time to devote to the project to obtain all the benefits that are available through pollution preventicm. This cannot be a fill-in task to do only as time exists. It must be. a high-priority, major responsibility for the leader with other responsibilities being removed or at least minimized.

5. Upper Management Support

A successful pollution prevention project requires the project team to challenge all aspects of the facility’s operations. This indudes reviewing product design, purchasing procedures, production techruques and maintenance pradices. Procedural. items are as important to address as the more technical equipment issues. Without strong upper management support and communication to all affected individuals of the goals of the work, turf battles are inevitable. A cammitment from upper management is reguwd to focus aIl facility efforts into a cooperative ~tute. The project leader and project team members also need to be sensitive to turf concerns and address them as they emerge. It takes a special talent to work with the variety of persons in any manufacturing facility and have them seriously review how they can change their ways to prevent pollution.

Upper management support js represented differently in different facilities. For some plants, it is most effectively presented by plant management presentations at production meetings. At other facilities, written policy statements are the normal mode of communication. In any case, there needs to be a method of two-way communication. This can be achieved through intemiews by the project team, by the use of suggestion boxes or by other methods.

6. Project Team Building

A team is used to allow several tasks to be completed concurrently by different individuals with different skills. There have been instances where pollution prevention plans have been developed and implemented without the foxmation of a team. This, however, appears to be an exception to the norm and was the result of certain highly skilled and highly motivated individd assuming pollution prevention responsibilities.

The team must be a workable size. While all departments within a company must eventually partiapate in the implementation of the plan, each does not necessarily need to be represented on the project team One approach is to keep the team small and involve other departments through interviews. A team size of three to five members is very workable.

Skills represented on the team should include &ent knowledge of the products produced, environmental considerations, maintenance issues and manufaduring requirements.

External members of the team are often beneficial as a means of providing new viewpoints. In a multi-facility company, an external member can be from another plant or from the corporate groups. He or she can also be an individual not employed by your company, such as a paid condtant. If an environmental ccnmdtant is used, it should be a firm whose emphasis is on p&tion prevention rather than end-of-pipe treatment methods.

For the case study of Xn Equipment Company, the project team has an engheer as the project leader and indudes a product designer, the facility en- coordinator, a maintenance supemisor and the production supetvisor of the plating department. The team has been authorized to contract with outside groups as necessary to provide assistance on spedfic issues.

7. The Assessment

Once the team is established, its purpose cammunicated throughout the organbtion and the leader determined, the team can proceed with the facility assessment. The objective of the assessment is to develop a firm understanding of what hazardous materialsareusedintheplant,whereth~areusedandwhereth~endupafterthe product is made. This idomnation is most easfy presented in a series of calculations called mass balances. These mass balances are developed under the premise that all hazardous materials entexing the fa* must come out somewfiere, whether in the finished product, in solid waste removed froan the plant, in the wastewater or m air epLissioM. Since we are loohg to modify individual processes or operations, we must complete these mass balances for each hazardous constituent for each process or operation. If several very different products are manufactured in one process, separate mass balances should be developed for each product.

It i s important to emphasize that the assessment operation is generally not an evaluation procedure - it is a data gathexing phase. Only after the process information is gathered can the identification and selection of pollution prevention options begin.

l L d . u l F i i p d l u r i o o ~ G u i d . 7

This assessment starts by collecting a complete list of manufacturing materials used in the facility and the amounts of each of these materials processed. This list must not only include purchased chemicals, but also metal stocks and other raw materials which have the potential for discharge to air, water or ground. This inventory will be used to determine which processes use hazardous materials and have the potential to generate hazardous wastes and emissions.

Once the total use quantities are determined, the total amount of hazardous constituents can be developed using information contained on the material safety data sheets (MSDSs). It is important that the accuracy of the MSDS be confirmed with the chemical manufacturer. Both the chemical inventory and a file of current MSDSs are required to be maintained under OSHA Worker Right-T+Know and EPA SARA emergency planning and emission reporting regulations. Much of the information required for the pollution prevention analysis has already been accumulated for those facilities required to submit Tier I or Tier 11 or Form R reports under the SARA regulations. Metal finishers should have mass balances available for every process. When these are available, they should be reviewed for compieteness and accuracy.

In addition to the mass balance information, the unit cost of raw materials, products and wastes should also be gathered for future economic evaluation of options.

For MSDSs that appear incomplete or suspicious, it is worthwhile to contact the material suppliers to obtain additional information on any hazardous constituents in the goods.

For our example facility, inputs and outputs will be tabulated for the cleaning, painting and plating operations.

8. Cleaning

Reviewing the vapor degreasing cleaning process, the inputs to the operation include the following:

Machinedparts Oil A, metal chips and shop dirt on parts Sheet metal Oil B and shop dirt on sheet metal Solvent Water absorbed from the air

Outputs from the cleaning operation include:

Cleanedpatts Cleaner sheet metal Spent solvent Tank sludge Air emissions

TCE usage and waste infonnation is obtained &om purchase records, waste records, MSDSs and waste analyses. Mormation is not typically available on air emissions, but this can be calculated if all other inputs and outputs are known using the following calculation:

TCE in = TCE out

TCE in = (Lbs. TCE used) x (% TCE in raw material) + 100

TCEout=(Lbs.TCEwaste)x(%TCEinwsste) +lOO+(Lbs.TCEinair emissians)

In this case, the pounds of TCE purchased are known from purchasing records and the pounds of waste generated are known from waste manifests or billing information. These figures need to be a d F e d to an annual basis. The amount of the hazardous constituent in the raw material can be found on the MSDS. The concentrations of hazardous constituents reported on MSDSs should be confinned with the manufacturer of that chemical. In this case, we are purchasing 100 percent TCE. A facility should know the composition of the waste it generates; if this infonnation is not in facility records, the waste contractor can often supply the data for a small fee.

The air emissions can be calculated by filling in the blanks in the equation and solving for the pounds of TCE emitted.

The oil removed &om the parts may also be reviewed, especially if one of the goals of the pollution prevention prognrm is to reduce the oily waste generation. In our case, we are only addressing the processes within the facilie and so the amount of oil coming m on parts is outside the scope of this work.

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9. Painting

Reviewing the solvent-based painting process, the inputs to the process are the following:

Sheet metal Paint, containing xylene as solvent

Clean booth filters xylene thinner and solvent

Outputs from the process inchtde:

Painted parts Waste paint Waste solvent/paint mix Dirty booth filters Air emissions

For this operation, the hazardous material of concern is the xyiene solvent. i

Xylene usage and waste information is obtained from purchase records, waste records, MSDSs and waste analyses. Information is not typically available on air emissions, but this can be calculated if all other inputs and outputs are known using the following calculation:

w Xylene in - Xylene out b Xylene in - (Lbs. paint used) x (% xylene in paint) + 100

+ (Lbs. thinner used) x (% xylene in thinner) + 100 b Xylene aut = (Lbs. paint waste) x (% xylene in paint) +lo0

+ (Lbs. solventlpaint mix waste) x (% xylene in solvent/paint mix) + 100 + (Lbs. booth filters) x (% xylene in booth filters) + 100

+ (Lbs. xylene in air emissions) In this case, the pounds of paint purchased are hown from purchasing records and the pounds of waste generated are known from waste manifests or billing information. These figures need to be adjusted to an annual basis. The amount of the hazardous constituent in the raw material can be found on the MSDS. Agam, a facility should h o w the composition of the waste generated. If this information is not in fadlity records, the waste contractor can often supply the data for a small fee.

As with the cleaning process, we can calculate air emissions if we know all other fisures. Typically, the solvent concentration in the booth filters is negligible, leaving only the paint and waste information to be collected.

It is possible that air e&on data has been gathered from air permit testing, allowing estimation of releases using another method. Typically, air permit testing calculates the pounds of solvent that could be released if the booth were being used at all times. If the booth is in constant use, these numbers may be directly applicable. If the booth is used periodically,~you need to correct for actual production time to obtain the expected annual releases. This is done through the following calculation:

W Estimated actual emissions =

(Full production releases) x (Actual hours production) + (Full production hours)

lo. Plating Plating is a more complex process in many regards than solvent cleaning or paintjng. In this example, we have three hazardous constituents of context zinc, cyanide and chrome. Here, we are looking spedfically at the plating process. Wastewater treatment is a totally separate process which just happens to receive all of its primary inputs from the plating process.

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Hazardous constituent inputs to the plating operation include:

b zinc Zinc anodes Zinc cyanide

Zinc cyanide Sodium cyanide

chtomic arid sohrtion

b Cyanide

b Chrome

Outputs from the plating process include:

b zinc Bath filters Wastewater Plated on parts

Bath filters Wastewater Gas (oxidized to CO, or carbonates in bath)

Bath dumps Wastewater Coated on parts

b Cyanide

b Chrome

Asanewmpb,theaassbalanceonzincfortheplatingprocesswouldbeasfallows:

Zinc in = (Us. anodes used) x (% zinc in anodes) + 100

+ (Lbs.zjnccyanideused)x(%zincinzinc+e) + 100 w Zinc out = (Lbs. bath filters) x (% zinc in bath filters) + 100

+ (Lbs. wastewater generated) x (% zinc in wastewater) + 100 + (Lbs. dnc plated on parts)

The pounds of zinc plated on the parts can be calculated by taking the total surface area of parts plated times the thickness of the zinc deposit times the density of the plated product times the percent zinc in the plated material.

Now that the mass balance infoxmation has been calculated, options need to be identified, evaluated, and prioritized.

11. Identifying Options

The assessment already conducted by the pollution prevention project team has identified a number of processes and operations which contribute to the overall plant wastes and emissions. The mass balances indicate the relative significance of each process as a source of these wastes and emissions. The next step is to wa.lk through each process or operation and idenbfy all options that could reduce or eliminate the wastes and emissions at their source.

While this evaluation is typically conducted on a process-by-process basis, a broader view should be considered when iden- options. For example, if cleaning is required because parts are supplied containing oils which must be removed, then eliminating the use of the oil in the previous process should be a option for eliminating the cleaning process. Likewise, if the oils are applied to the parts to prevent them from Nsting while they sit in storage, then implementing just-in-time manufacturing is a pollution prevention method to eliminate the use of oils and subsequent cleaning.

The key to identdymg pollution prevention options is to repeatedly ask one question - why. Why do we clean?, Why do we paint?, Why do we plate? While this seems overly simple, it does in fact work as long as you keep on asking why, until you get to the source of the problem.

There are different levels of issues to address when asking why. The &st level is the basic questions noted above which challenge the product design. After these are addressed, a second level of questions can be asked which cover the processes, procedures and equipment used to make a product. Examples of these questions are Why do we use solvent in the paint?, Why do we store a six-month supply of parts?, Why do we remove the oil with TCE? and so forth.

This practice of asking why is one method of id- pollution prevention options. A second method is to explain the overall pollution prevention goals to the operators, product designers, process engineers and maintenance personnel most involved with the processes and operations and to solicit their input on how things could be changed to reduce wastes and emissions. These internal resources are extremely valuable and well worth the additional c o ~ g that may be required to assure people that their ideas will be taken seriously.

At this point you should be idenhfymg all possible options. You should not be eliminating or discounting any serious proposals no matter how far-fetched they hitially seem. Having a list of ten outrageous ideas may help someone come up with the eleventh wild idea that actually tums out to be worthwhile.

Outside resources should also be tapped to assist in identifying options. Examples of external resources include:

Corporate or sister plant personnel Equipment vendors Chemical and material suppliers Trade associations

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M a r l F i i P o l l u t i o c l ~ G u i d . l2

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These concepts are no different from the procedures used to purchase any major piece of equipment, except you are essentially purchasing expertise. It is helpful to select a consultant that understands your operations and can work with the people in your

consuitants State Technical hsistance Programs (T’APs) State reportdgrants Universitiesltrade schools EPA - Pollution Prevention Information Clearinghouse

For companies with multiple facilities, representatives &om other plants or from corporate offices can provide a new source of ideas for pollution prevention options. These personnel may have experience in testing a specific option with the product being manufactured.

Equipment vendors and chemical suppliers are often an excellent source of infomation on alternatives. They should not be used as a slngle source of information, however, since many vendors have a short-term motivation to sell a particulat product. A rare few vendors work with a long-term goal of obtauung your business by helping you d e a better product more efficiently.

Trade associations are another valuable source of infomation and should be used whenever possible. Examples indude the Minnesota Association of Metal Finishers, the Chemical Coaters Assodation, and the Assodation of Electroplaters and Surface

ideas. . Finishers. The American Institute of Plant Engineers can also be a valuable source of

State and federal agencies and universities can also be tapped as a source of information on alternatives for common operations. The Minnesota Technical Assistance Program (MnTAP), is a nonregulatory program at the University of Minnesota, School of Public Health. Funded by a grant from the Minnesota Office of Waste Management ( O w , MnTAP was created in 1984 under a legislative mandate to work cooperatively with Minnesota businesses toward implementation of pollution prevention, waste management and related en- protection iniatives. MnTAP has a deannghouse of publications available to assist businesses with their industxial waste issues.

The EPA and some states have on-line computer systems which contain summuies of pollution prevention case studies and projects.

Consultants can be an excellent source of information, especially if they specialize in the

substantiallylesstimethancanyourownuntrainedstaff. Hiringaconsultantisanew task for many facilities, but there are several suggestions to keep in mind.

. area you are inves@ating. consultants may be able to do certain activities in

Have a dear scope of work Obtain competitive proposals Investigate the consultant’s qualifications Make the consultant do what they said they would do

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facility. It is especially important that the consultant provide an educated outside view of your operations in order to come up with new ideas.

12. Evaluating Options Once a list of options has been developed, the team must evaluate those options which can address each waste or release and select options for implementation. The goal at this stage is to i d e n q the product, procedure or equipment modifications that will best reduce or eliminate the waste or emission at the company.

Obviously, the elimination of waste is not the only factor to be reviewed in this process. There are a great variety of factors that need to be cansidered when evaluating options. Each fa* will have Werent considerations as to which factors are most important, and these need to be established in order to determine which option is best for the plant. Examples of evaluation factors include:

Capital cost and availability Operating cost Savings Envitonmental impact, both short- and long-term Occupational hazards impact Labor requirements or savings Maintenance requirements or savings Energy requirements or savings Technical risk Product changes required and customer approvals Process changes required Additional facility changes required Production shutdown requirements Technical support required and available Implementation schedule

These factors can be combined into two general categories, t e c h i d issues and economic issues. Obviously, both are important to assure a successful implementation of the selected options. Typically the technical evaluations are conducted before considering economic issues.

W. Technical Evaluation

The technical review of the option indudes asking the following types of questions for each option:

Will it work in this application? Has it worked elsewhere in similar conditions? What are the potential problems? What are the labor and maintenance requirements? What results have others obtained?

The internal and external resources listed earlier in this paper can be used to obtain infoxmation for the review of options. Before recommending the purchase of equipment, you should view installations or talk with users of the equipment. This technical review of each option will id- many options that have a high likelihood of failure. Others will appear to have a high likelihood of success. Generally one's 'gut feeling' is a good indicator of whether a partidax option has been well researched. If you don't feel cdortable with a particuhr option, you need to evaluate it further.

Typically this technical evaluation can lead to one or two options which hold the most promise for accomplishing the fadiifs pollution prevention pals. While the identification of these options is typically obvious, in d i n s t a n c e s it maybe useful to use a rating system to compare various options. A good example of a weighted average rating system for pollution prevention projects is presented in the EPA publication,'Waste Mmuruza . . . tion opportunity Assessment Manual.' For this case study with the cleaning, painting and ph&g operations, an initial technical review of the ideas generated left these for further review:

b Product Use plastic or composite housing - eliminate painting Use alternative metals - eliminate plating

b Cleaning Purchase clean parts - alternative Nst protection,

minimize storage time Modify&

I Use alternative solvents Use aqueous cleaning Use mechanical cleaning

' b Painting Purchase prepainted parts Improve transfer efficiency - process . m o d i & a t i o n s Minimize number of cleanups required Use high solids solvent coatings Use water-based coatings Use powder coatings

Plating Use alternative processes - vapor deposition Use nOIlcyanide plating Use alternative coatings Use bath dragout reduction Use bath dragout recovery Use water conservation Use metal recovery

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The technical review identified several advantages and disadvantages of each option. For example, changing the product to use plastic housings was discarded based on the amount of time and effort that would be required to make and approve the modifications. Switching from the vapor degreasing system to another m e of solvent was seen as not having adequate environmental benefits. As a result of this review and evaluation, the following options were identified as those most technically feasible for the facility:

b Cleaning - Aqueous cleaning system Painting - Powder coating system

b Plating - Use of noncyanide alkaline zinc process with bath dragout reduction

These options were then reviewed for economic impact.

14. Economic Evaluation

The economic review of pollution prevention options is generally no different than the typical economic reviews conducted for any capital expansion at a facility. In the review of capital funding for a pollution prevention project, some fadties apply a lower .standard for the required payback or return on investment. This is done in an attempt to account for the numerous intangible benefits of pollution prevention.

Different sizes of projects typically undergo different levels of sautiny in a fadlity. For a project requiring $2O,OOO in initial capital funding, a simple letter format explaining the project costs and benefits may be acceptable. For medium-sized projects this review will contain estimated operating costs and savings and will calculate a simple return on investment. For large projects the economic review incorporates equipment depreciations and expected equipment usages and may calculate a n i n t d rate of return on the investment. What level of economic review is required for a particular f a d Q project is usuaIly well defined. The reviewer needs only to obtain the proper information and complete the proper forms.

Obtaining the information necessary to conduct the economic review is not always an easy task. Both the capital and operating costs must be developed as well as the expected savings. While vendors can supply much of this information, the numbers must be reviewed by the faality to ensure that it accurately represents the expected costs and benefits for the plant. This review should again utilize the internal and external resources identified earlier in this guide.

All pertinent costs of a process or operation must be taken into account. These include:

chemical costs

maintenance costs permitting costs

utility costs

disposal costs

The savings associated with a particular process or operation include not only the differences in the above costs, but also selected avoided costs. These avoided costs may be deueased hazardous waste taxes or taxes associated with emissions. It is important not to overlook these cost savings.

A common mistake is to only look at the capital cost of a process and to w o r e the others. One of the most difficult things to put a cost to is that pertaining to environrnental liability.

The simple payback period for a project can be calculated by:

b Payback @ears) = capital Cost + Yearly savings

15. Prioritizing options

At this point all of the pollution prevention options have been identified, evaluated and selected for all of the processes, wastes and emissions. In any real facility there are limited personnel and financial resuurces which prevent all options from being implemented at the same time. The last part of the review, therefore, involves prioriiizing the various selected modifications. Several factors are used to priorilize the projects available for a faciliv. Each factor presented below will have a different importance for different facilities. If capital is not readily available for a plant, then low-cost items will be done before capital-intensive projects, regardless of the envimnmental impact. If obtaining immediate results is important, then a project which may encounter an extensive permitting process will not be favored.

One of the key factors is the environmental and economic srgnificance of the option. An option that has a high environmental impact, such as ehmahng the use of chlorinated solvents, will be preferred Over one that w d d reduce wastewater sludge volume by 10 percent even though the wastewater project may have a higher return on investment.

Projeds that have a higher technical xisk or require significant technical support may not be appropriate for a fa* with limited technical staff. This issue is often a concern at d e r facilities and can make an ecoIlomicaIly sound option unfeasible until adequate technical support is available. Edislmg outside asistance may be the most cost-effective way of completing this task.

S w n g Abilities

Some projects require additional attention from manufacturing or maintenance staff for startup and initial operation. This factor can be a concern and may reqyire

If major product or process changes are planned for a facility, it may make sense to delay implementation of certain projects and incorporate them into the planned changes. For example, it would not be wise to invest in a dry powder coating system as a solvent paint replacement if the facility planned to change to plastic P"

Ease of M0aif;cLltiOns - Custarcr Role Some customers, such as the military and automotive manufacturers, require that any major product revisions be approved prior to being installed. This review process can take many months and a good deal of labor. A company may select to wait on proposing certain modifications until other modifications are also desired to minimize the number of customer approval projects.

AoaiIabilify of Capital

For plants with lean capital budgets, this factor is extremely important. Often facilities operate with minimal capital expenditures for a Iimited amount of time. During this time efforts can focus on low-cost projects, with larger projects delayed until better economic times.

Identification of pollution prevention options is best accomplished using the 'controlled brainstorming' technique presented here. Both internal and external resources need to be tapped to develop a comprehensive list of options which can then be evaluated. Soliating ideas from all personnel who will later be involved in the project implementation also helps them to feel a part of the overal project and contributes to later success.

Selecting options for implementation is done by evaluating the technical and economic merits of each reasonable option. Plant-specific concerns are used to evaluate and select options. Technical and economic evaluations are completed using the same list of resources used to generate pollution prevention options.

P r i e g options is done to determine which of the selected options should be addressed first. Prioritization considers a variety of factors including the project significance, the technical feasibility, st- requirements, antiapated product changes, customer requirements and availability of capital. Once items are prioritized, an overall fadlity plan can be developed and projects implemented.

The results of the waste redudion assessment can be used to prepare the facility pollution prevention plan.

C. PREPARING A POLLUTION -ON PLAN A pollution prevention plan, integrated into a facility's business plan, is an effective method of evaluating how fadlities are dealing with environmental issues. Such a plan may work to decrease waste disposal costs, lower potential liabilities, increase worker safety, ease the environmental regulation compliance burden, decrease negative publidty, improve manufacturing effkiencies and provide guidance in allocating financial and personnel resources. The contents of the pollution prevention plan for Minnesota facilities must include the following:

Policy statement that includes upper management support of the program. Description of current waste- or emissicm-generating processes. Description of current and past practices used to eliminate or reduce the generation of toxic pollutants, as well as the effectiveness of these practices. Identification of poUution prevention options which are both economically and technically practical for the reduction or elimination of pollutants. Pollution prevention objectives with numeric goals. Rationale used to develop each goal. Options which are not economically or technically feasible. Certification statement verifying the accuracy of the information contained in the Plan-

Poticy Statement

The policy statement must affirm upper management's support for eliminating or reducing the generation of t& pollutants by the fadity. One possible policy statement is presented below:

'At koalpgny name here). protecting the environment is a high prioriv. We pledge to eliminate or reduce at the suurce of generation, recycle or reuse on site all materials which result in the generation or release of hazardous Wor toxic pollutants to the environment where such activities are judged to be both technically and economically feasible.'

2. Description of the Generating Processes

The &st step in developing any type of plan is to establish a baseline. The baseline typically used is reported volumes from speaed years of RCRA wastes generated, of SARA 313 emissions or of state-listed wastes generated or emitted. In such cases as above, determining the baseline is a matter of tracking down the appropriate paperwork (waste manifests and Form R reports, for example). Where no baseline criteria exist, the facility must establish them. The criteria selected should be measurable, should reflect the facility's activities and A d d include all the hazardous or toxic mat& the facility Uses.

The description of the current processes and operations can take the form of a black box diagram. A black box is an arbitrary boundary which can be drawn around a facility, a manufacturing process or operation, an individual tank or machine. In selecting where

I

a boundary is to be drawn, it is important that materials crossing the boundary can be identified and quantified in a mass balance equation.

Materials which uoss the boundary are broken down into inputs and outputs. Inputs include raw materials and fuel. Raw materials can be further broken down into those which form the final product and those which are ' o t h d e used. ' Examples of raw materials which fall into the 'otherwise used' category include cleaning solvents, etchants, coolants, oils and catalysts. outputs include products, byproducts, wastes and emissions. If all materials crossing the boundary have been identiiied, then the mass balance equation will take the following form:

Inputs = Outputs + Accumulation For most situations accumulation within the black box process is assumed to be neglible.

By using this black box approach, processes and operations can be more easily defined. The process description would then include a description of the activities occurxing within the black box, the inputs to the box and the outputs from the box. This w e of methodology should be used on all the processes covered under the pollution prevention plan.

3. Description of Current and Past Pactices

A description of current and past pollution prevention efforts is important for two reasons. First, such a description documents past activities in the event that conditions change or an idea resurfaces at some future date. This helps prevent work from being repeated unnecessazily and provides the groundwork for feasibility studies of similar work. Second, this documentation is useful to facilities which have adopted a proactive approach to pollution prevention. Gains m pollution prevention can, for instance, benefit public relations.

4. Investigation of Options

Investigating the available options is very similar to a brainstonning session in which ideas should be soliated from as many sources as is practical for the size of the project. Judgment on the feeasibdity of each idea should be made only after considering all aspects. In developing options, several areas should be considered: raw m a t e d substitutions, product design, waste segregation, employee training, housekeeping, process modScations, on-site recyding and reuse. .

In addition to internal resources, a number of external resources are available to assist in developing options. Several of these resources are listed below:

Trade journals Professional organizaticms Vendors, both equipment and chemical Minnesota Technical Assistance Program (MnTM) Minnesota Office of Waste Management Universitieslcolleges

consultants 5. Feasibility

Both the technical and economic feasibility of the options presented in the previous section are addressed as a part of a pouutian prevention plan, Minnesota pollution prevention planning req&ements allow an option to be rejected on either technical or economic grounds. In considering the technical feasibility of an option, a number of details need to be addressed, including pollution prevention, quality, production rate, risk, and worker health and safety.

In considering the economic feasibiliiy, most companies have some method of evaluating a project's economics. Typical methods are return on investment (ROI), payback years, net savings or internal rate of retum (IRR).

6. Development of Goals

The Minnesota Toxic Pollution Prevention Act requires that the facility establish pollution prevention objectives. Where a facility is not in a position to set objectives, they must state how they will proceed in developing these. Such objectives should be -related to the current toxic pollutants generated or released as either a percentage reduction or as a reduction in the total volume or weight. In considering these objectives, it is important to remember that the amount of toxic pollutants generated is often closely related to production. Where possible, the plan's objectives should be tied to production to prevent under- or over-reporting of the progress made. It is also important to be realistic in developing these objectives and not set them based solely on

may reduce the actual progress made; these should be taken into account in setting objectives. Any calculations, assumptions or rationale used in setting these objectives should be documented in the plan.

manUfacturers'daimSorbest~ mndiths. Start-up problems and 'the real world'

7. Measurement of Progress

As difficult as it is to measure the volume of generated toxic materials, measuring the amount of progress made is even more difficult. Variations in production can mask or swell any actual gains made in pollution prevention. While a number of measures of production exist, they were generally developed to gauge production for different reasons. Several of the measures which are generally available include: sales, units produced, square footage produced, raw materials used, number of employees and direct labor hours.

Selecting a method of measuring production to include in a pollution prevention plan requires that the individual circumstances of the facility be taken into account. Each of the measures of production listed above contain inherent strengths and weaknesses. Sales figures are readily available; however, they vary with inflation, and changes in inventory also will affect the accuracy. Units produced, square footage produced and raw materials used are probably the best methods of relating production to wastes and emissions; however, for plants which produce a large variety of products, it can be difficult to produce accurate comparisons if the product mix changes. The number of i

employees or direct labor hours can help smooth out any variation in product mix, but is affected by changes in productivity or automatioi

8. Annual Progress Reports

Pollution prevention progress reports are required in Minnesota and must be submitted to the State by October 1 of each year. Required components of these reports include:

Certification that a pollution prevention plan has been prepared, is accurate, and is

Summary of each objective or plan goal. Numexic or non-numeric objectives and schedules for meeting objectives or goals. Summary of the progress made during the year, if any. Methods used to achieve this progress. An explanation of why the objectives or goals were not achieved, if necessary.

Any explanation of why the objectives contained in the plan were not achieved should include a discussion of the barriers encountered. Such barriers could indude technical, economic and regulatory hurdles.

signed by a company officer and phnt manager.

,For more infomtion, consult the Minnesota Guide to Pollution Prevention Planning, available from the Minnesota Office of Waste Management.

D. POLLUTION PREVENTION BIBLIOGRAPHY

Waste Minimiration O p p M n i f y Assessment Munual, U.S. Environmental Protection Agency, EPA/625/7-88/003, Hazardous Waste Engineering Research Laboratory, 1988.

Guides to Pollution Prevention - The Mefa2 Finishing Industry, U.S. Environmental Protection Agency, EPA/625/R-92/011, Hazardous Waste Engineering Research Laboratory, 1992.

Minnesota Guide to Pollution Prevention Phning, Minnesota Office of Waste Management, March 1, 1991.

State Legtslntion Relnting to PoZlutian Prepention, Compiled by Waste Reduction Institute for Training and Applications Research, Inc., April 1991.

The Minnesota Pollution Preomfion Ad, Requirements for EIedroplaters and Surface Finishers, Larry IC. Sib&, November 5,1990.

Waste MinimizatiMoZlution Prevention Regulations, Kelly Gilliland, Proceedings of National Conference: Minimization and Recycling of Induskial and Hazardous Waste, 1992

Pollution Preocntion - Identi&ng, Selecting, and M f i z i n g Opfias, Daniel P. Reinke, P.E., Proceedings of National Conference: Minimization and Recycling of Industrial and Hazardous Waste, 1992

pnparing a Pollution Prevention Plan, Larry K. Sibik, Proceedings of National Conference: Mmmzation and Revcling of Industrial and Hazardous Waste, 1992. . . .

US EPA Pollution Prepention Information Ckd@owe, US EPA, EPA/600/9-89/086.

SECTION 11. ELECTROPLATING

Typical processes in electroplating indude electrochemical and electroless plating, anodizing, degreasing, deaning, pickling, et-, and coating. These processes generate waste streams such as spent process baths, contaminated rinsewaters, treatment sludges, and degreasing solvents. This section addresses the reduction in generation of these wastes through source reduction measures such as improved process control and substitute chemistries. Alternative recovery and treatment measures are also addressed.

A. SOURCE REDUCIION

1. Drag-out Reduction

Process chemical drag-out is the primary source of chemical contaminants in rinsewaters. These rinsewaters require treatment to remove the harmful constituents before the water is reused or discharged. Minunipng the amount of process chemicals dragged out of process baths minimizes not only the amounts of chemical additions to fhe bath but also the mass of contaminants that need to be removed from the rinsewater. There are several process modifications that are effective in minimidng drag-out: -

Workpiece withdrawal rate Drain time Racking orientation Drip boards Spray rinses Air knives

Wurkpece withdrwd rate

Workpiece withdrawal rate will influence the amount of solution ramaintng on the workpiece. The more slowly a workpiece is withdrawn from a process bath, the thinner the chemical film on the workpiece and the lesser the drag-out will be.

Longer drain time over the process solution allows more drag-out to be retuned to the bath.

Racking

Drip boards catch process chemicals that drip from workpieces as they are transferred between process tanks. The boards are slanted such that the drag-out is retumed to the process bath from which it came.

Spray rinses can be used above any heated process tank to recover drag-out before it is t r a n s f e d to the next tank. The sprays rinse drag-out from the workpieces as they are withdrawn from the process tank. A spray rinse is equivalent to approximately one-half of a rinse. Spray nozzles can be sized and water flow rates adjusted such that the spray rinse water makes up for evaporative losses. Deionized water should be used in spray rinses.

Air knives

Air knives are used to blow air onto the d a c e of the workpieces as they are withdrawn from the process solution. The mechanical action of the air effectively blows the drag-out solution back into the process tank.

Further information on the use of these te-es is given m Section VII, 'Water Consemation and Rinsing.'

2. Chemical Process Control

Proper control of bath operating parameters can result in more consistent bath operation and part quality as weIl as in longer bath life. The strategy is simple: determine aitical operating parameters and maintain these parameters within acceptable limits. Examples of aitical operating parameters are:

1

constituent concentrations

temperature contaminant concentrations

PH

Two examples of critical operating parameters are cyanide-bzinc ratios in zinc plating baths, and pH in chromate baths.

3. Bath Purification

The best approach to bath purification is to avoid contamination. Some examples of this approach are the use of deionized water for make-up, adequate pre-rinsing of parts, and using lined tanks.

Puri6ication of process baths will remove impurities that inhibit the proper operation of solutions, thereby increasing the life of the solution. purification measures include:

Media filtration

Ion exchange Electrolpc @cation Carbon treatment Chemical treatment

Media filtration

Media filtration is used to remove suspended impurities h n process solutions. If these suspended particles are not removed, they can cause plating defects as the particles may be attracted to the dean workpiece as it is immersed in the process solution. Accllmulations of particles on the bottom of a process tank can lead to shorter bath life. Proper filtration sizing and media selection are dependent upon the following factors:

- Adequate pump capaaty A tum-over rate of 2 to 3 tank volumes per hour is typically adequate for effective, continuaus filtration. A pump should be sized such that adequate throughput is provided over the entire filtration cycle. The pressure differential aaoss the filter media will increase as solids build up. A filter media is usually changed when the pressure differential reaches 35 to 40 psi.

- Adequate Media Selection of media type is important to effect adequate filtration with a minimum of maintenance and waste disposal. Wound cartridge filters and paper disc filters are the norm for filtering plating solutions. There are permanent disc filters available which decrease the volume of filkation waste for disposal. These units have plastic discs which must be cleaned once they become loaded.

- Adequate solids-holding capaaty Use the largest micron size possible with a particular process solution in order to maximize the solids-holding capaaty. Suspended partides in plating solutions are typically under 100 microns.

- Adequate filter area A minimum of I ft2 of filter area is typically required per 25 gph throughput for add baths or per 15 gph for alkaline baths.

I o n exchange can be used.to remove dissolved inorganic contaminants from a process bath with minimal disturbance of the process. Selection of the proper resin type is the most important consideration in using this technology. Typical plating bath conditions involve high concentrations of dissolved solids, extreme pH conditions, and the presence of strongly oxidizing compounds which can not only

retard the p e r f o m c e of ion exchange but can also cause degradation of the resin. This technology has been reported to be successful in the purification of the following baths:

- Trivalent Chromium Zinc, nickel, lead, and copper have been removed kom trivalent chromium plating s o l u h a s using ion exchange. The continuaus nature of this treatment al lows the maintenance of a constant imm level which results in a constant plate quality.

- Anodizing Ion exchange has been successful in removing aluminum from sulfuric add anodizing solutions. Without purification, the aluminum level builds to a point where the bath does not operate properly and must be disposed of. The continual removal of aluminum from these solutions allows a consistent quality level to be maintained and avoids the downtime and disposal and make-up expenses incurred when the bath is dumped.

- Chromic-add based solutions Cationic impurities have been removed from chromic acid anodizing solutions, chroxnates, and chromic add rinses as part of an evaporative recovery system. The highly oxidative nature of concentrated hexavalent cluomim solutions is typically detrimental to resin life. Highly chemical resistant resins have been f developed to attempt to address these concerns.

- Piding solutions Ion exchange has been successful in removing iron from hydrochloric and nitric adds.

Electrolytic purification removes dissolved inorganic metallic impurities from plating solutions through a process hown as 'dummying'. Contaminants such as copper are plated out from a plating solution at low current density. The low current removes the copper but does not affect the bath additives.

Carbon treatment removes dissolved organic impurities which enter process solutions through drag-out from cleaning operations. Organu: impurities which can be dragged into a bath include buffing compounds, maduning hbricants, and surfactants. The plating bath itself can contain wetting agents and brighteners that can decompose due to the temperature, pH, and electrode reactions encountered in the solution. These organic impurities can adsorb onto the surface of a workpieces causing coarse deposits and poor adhesion. These dissolved compounds can not be I

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- Application method Batch treatment. Carbon is added directly to the process solution in a separate tank. Agtation is provided with a contact of tirne of at least 60 minutes being adequate. The carbon is settled, and the solution is filtered back into the process tank. Heating the solution can inuease the adsorption rate.

rn Pre-coat on filter and filter-aid. Carbon is added to a filter over the pre-coat filter aid. This method can be used as a continuous treatment without shutting down the plating line.

Pre-packaged &on charge. Carbon is either attached directly to a filter or is contained in a chamber which is attached to the filter system. This method can be used as a continuous treatment method.

- Dosage Typically, 1-2 pounds of activated carbon are used per 100 gallons of process solution. Proper dosage can be detexmined through use of Hull Cell tests. Minimizing the amount of carbon used will minimize disposal costs.

- Enhancements The addition of 35% hydrogen peroxide solution @or to carbon treatment is hefpful for precious metal and +e copper solutions. The hydrogen peroxide oxidizes organic compounds to a less soluble form. A dosage of 4 ml per gal of plating solution is usually adequate, but proper dosages should be determined through Hull Cell testing.

Chemical treatment removes dissolved inorganic impur i t ies from a solution by the addition of chemicals which cause the impurities to become insoluble and precipitate. The precipitate is then removed by filtration. Some typical applications:

- Lead and cadmium removal using polysulfide - Copper removal using -zinc dust - Conversion of hexavalent chromium to trivalent chromium using sodium - Carbonate removal from cyanide-based baths using barium or calcium salts hydrosulfite

I

Carbonates are also removed from cyanide-based solutions by c h i k g the solution to between 30°F and 40°F. This process can be performed in a batch mode or on a continual basis.

4. Alkaline Cleaners

Many alkaline cleaners contain chelators such as ammonia, gluconates, giucoheptanates, phosphates, citrates, and ethylenediaminetetraacetic add (EDTA). Dunng bath operation, these compounds act to hold metals in solution. These matexials may be present ZLS water COnditiQners to tie up calcium and magnesium in hard waters or they may be present to enhance the cleaning mechanism.

These chemicals can atso hold metals in solution during treatment, which can res& in a more involved treatment process as well as an inueased amount of sludge generation. Alkaline cleaner solutions can be formulated without chelating compounds which can simplify their treatment and decrease sludge generation,

The water used for initial make-up and daily additions is also important to the operation of alkaline cleaners. Using soft water for make-up will eliminate the potential of precipitation of calcium and magnesium salts and their contribution to sludge .generation. Chemical components that may be part of the cleaner formulation stcictly as water conditioners ( h o r n as sequestering agents) can be eliminated if soft water is used, which should optimize bath life and allow easier treatment.

5. Cyanide Process Bath Alternatives

- AlkalineZinc This solution is based on sodium hydroxide and plates best on regular and leaded steel substrates. Low chemistry baths operate at 0.8 to 1.2 Ounces per gallon (opg) (6.0 to 9.0 g/L) zinc; high chemistry baths operate at 1.8 to 3.0 opg (13.5 to 225 glL) zinc. Proper control of bath parameters and excellent predeaning are essential for successful use of this solution.

- Addzinc This solution is based either on ammonium chloride, potassium &hide, or a combination of both. Suitable substrates indude reguiar and leaded steel as well as cast iron, high carbon steel, and heat treated and carburized substrates. Typical ammonium chloride-based baths operate at 2.0 to 4.0 opg (l5 to 30 g/L) zinc, while the potassium chloride bath operates at 3.0 to 5.0 opg (22.5 to 37.5 g/L) zinc. These solutions require colrosion-resistant equipment, excellent precleaning, and proper parameter control.

Zinc alloys are discussed under 'Zinc and Cadmium Process Alternatives'. !

M

Gppm

- Alkaline Copper These solutions are based on proprietary complexing agents. Suitable substrates include steel, brass, and zincated aluminum. Some solutions are recommended for zinc die cast substrates. Typical baths operate at 1.0 to 2.0 opg (7.5 to l5.0) copper. The low copper concentration requires agitation, which can be medranical, pneumatic, 01 ulh.asanic. Plating speeds are typically slower than cyanide copper. The deposit is very h e grained and is suitable as a heat treat mask at lesser thicknesses than those obtained with a cyarude copper bath.

- Add Copper These solutions are sulfuric add-based. Suitable substrates indude plastic, and steel and zinc die cast only after a copper or nickel strike. Typical baths operate at 10 to 13 opg (75 to 97.5 g/L) copper, while the high throwing printed circuit bath operates at 3 to 5 opg (22.5 to 37.5 g/L) copper.

- Copper Pyrophosphate

Cadmium

Cadmium plating baths based on sulfate, fluoborate, and perdorate chemistries have been developed. In corrosion tests for the relatively new cadmium perchlorate bath, nonchromated test panels were free from white and red rust after 288 hours of salt spray*

Brass

There is an alkaline brass solution on the d e t which is based on potassium hydroxide and proprietary c o m p l e agents. S W I e substrates include steel and zinc die cast. Typical bath concentrations are 0.6 to 1.2 opg (4.5 to 9.0 g L ) copper and 0.2 to 0.3 opg (1.5 to 2.25 g/L) zinc. Agitation is required in this bath which operates at approximately 100°F.

Cyanide-based strippers are typically used to strip brass, bronze, copper, gold, nickel, and silver from steel and nickel substrates. Two of the more common cyanide-based shipping applications are the shipping of nidcel and copper from steel. The cyanide complexes the nickel or copper to prevent redeposition onto the workpiece. This nickel-cyanide complex is very strong, and not amenable to conventional chlorination. There are several proprietary noncyanide stripper

formulations on the market. The active ingredient(s) for several typical formulations:

- sulfuric add (electrolytic) - sulfuxic aad/m-nitrobenzene sulfonic add (immersion) - sodium hydroxide/ethylenediamine/m-nitrobenzen sulfonic acid (immersion) - ammonium hydroxide/sodium chlorite (immersion) Immersion strippers require the simplest equipment set up. Ventilation reguirements vary between the different solutions. Strippers with strong chelating agents will not form appreciable amounts of sludge in the tank. Those without strong chelators will form sludge which necessitates a more thorough tank dean aut between charges.

The stripper formulations are spedfic not only to the metal being removed but also to the substrate.

6. Zinc and Cadmium Process Alternatives

Zinc Alloys

- Zinc Nickel An alloy plating of zinc-nickel is suitable for high temperature corrosion protection. Salt spray corrosion resistance of the zinc-nickel plate (with chromate conversion coating) has been reported in excess of 300 hours to white i corrosion and in excess of loo0 hours to red corrosion. Suitable substtates include steel, cast iron, and carbonitxided surfaces. zinc-nickel can be plated from either acid or altatine solutions:

Add zinc-nickel baths typically yield deposits of 7 to 14 percer.: nickel. Typical bath concentrations are 7.7 to 8.3 opg (52.5 to 62.25 giL) zinc and 6.6 to 7.8 opg (49.5 to 58.5 glL) nickel. Equipment needs are similar to those for add chloride zinc solutions.

a Alkaline zinc-nickel baths typically yield deposits of 5 to 9 percent nickel. Typical bath concentrations are 1.1 opg (8.25 g/L) zinc and 0.2 opg (1.5 g/L) nickel. Equipment needs are similar to those for ;rkaline zinc solutions.

- Zinc Cobalt An alloy plating of zincxobalt is suitable for moderate temperature corrosion protection. Salt spray corrosion resistances (with chromate conversion coating) have been reported in excess of 200 hours to white corrosion and in excess of 400 hours to red corrosion. zinccobalt can be plated from either add or alkaline solutions:

w Acid “cobalt baths typically yield deposits of less than 1 percent cobalt. Typical bath concentrations are 4.0 opg (30.0 g/L) zinc and 0.25 to 0.5 opg

(1.88 to 3.75 g/L) cobalt. Equipment needs are similar to those for add chloride zinc solutions.

rn Alkaline zinccobalt baths typically yield deposits of less than 1 percent cobalt. Typical bath concentrations are 0.8 to 1.2 opg (6.0 to 9.0 g/L) zinc and 0.004 to 0.007 opg (0.03 to 0.05 glL) cobalt. Equipment needs are similar to those for alkaline zinc solutions.

- Zinc Iron An alloy plating of zinc-iron is suitable for ambient temperature corrosion protection. Salt spray corrosion resistances (with chromate conversion coating) have been reported in excess of 200 hours to white corrosion and approximately loo0 hours to red corrosion. Zinc-iron alloy plate is also used as a paint base. Zinc-iron can be plated from either acid or aIkaline solutions:

rn Acid zinc-iron baths typically yield deposits of less than 1 percent iron. Typical bath concentrations are 10.8 to 16.0 opg ( 81 to 120 g/L) zinc and 3.7 to 5.6 opg (27.75 to 42.0 g/L) iron. Equipment needs are similar to those for acid chloride zinc solutions.

Alkaline zinc-iron baths typically yield deposits of less than 1 percent iron. Typical bath concentrations are 2.7 to 3.3 opg (2025 to 24.75 g/L) zinc and 0.033 to 0.067 opg (0.25 to 0.50 g/L) iron. Equipment needs are similar to those for alkaline zinc solutions.

- Tinzinc An alloy plating of h-z inc is suitable for ambient temperature corrosion protection. Tii-zhc alloy plate is typically 70 to 75 percent tin and 25 to 30 percent zinc. A chromate conversion coating gives the optimum corrosion protection. The coating has good fri&onal properties b u t is susceptible to mechanical damage due to the softness of the deposit. Tin-zinc alloy is plated from add, aIkalkre, and neutral solutions.

This process is also known as vacuum metaUizing. Vaporized aluminum is deposited on the workpiece at very low pressures. The aluminum is deposited in a very thin coating which reproduces the exact contour of the substrate. The process usually involves the application of a base resin fill coating followed by the aluminum coating. Further protection of the surface is usually imparted by the application of a topcoat of lacquer or resin.

7. Hexavalent Chromium Process Bath Alternatives

Hexavalent chromium is used extensively in decorative and functional plating applications as well as in conversion coatings. Alternative solutions which do not contain hexavalent chromium are available for selected applications:

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Trivalent chromium plating solutions Trivalent chromium conversion coatings Nonchrome sealers

Trivalent chrome baths can replace hexavalent chromium baths in decorative chrome applications. Typical trivalent chromium baths operate at 0.7 to 3.3 opg (5.25 to 24.75 g/L) chromium and a pH of 2.3 to 4.0. This compares with chromium concentrations of 13.3 to 26.7 opg (lo0 to 200 glL) chromium and a pH of less than 1 for hexavalent chromium baths. The lower concentration of chromium in the trivalent solution results in less drag-out of chromium. There is virtually no mishg m the trivalent process. In using a hexavalent chromium plating bath, approximately 80% of the available power is used to generate hydrogen gas with resulting misting. Controls are or will be required on hexavalent chromium emissions as chromium is a hazardous air pollutant under the Clean Air Act Amendments of 1990.

Trivalent chrome conversion coatings are available to replace hexavalent clear chromate coatings. These 'chromates' typically contain trivalent chromium at low concentrations. The blueish c o l o r is formed by the adsorption of organic blue dye or by the oxidation of the trivalent duomiurn at the surface of the part.

Nonchrome sealers are typically one of two types:

- Inorganic salt-based. These are intended to replace true chromates and may be made up with nitric add.

- Organic-based. These are polymeric coatings which are designed to be used alone or in conjunction with other duome-based or non duome-based conversion coatings. The use of this coatirtg will improve the corrosion resistance of the workpiece.

RECOVERY AND TREATMENT AL'I~ERNATIVES

Precipitation

Hydroxide Precipitation

Precipitation of met