Removing Coatings and Cleaning Masonry

Substrates

Kenneth A. TrimberKTA-Tator, Inc.

Removing Coatings and Cleaning

Masonry Substrates- Webinar Learning Objectives

Identify SSPC/NACE, ASTM, and ICRI standards and guidelines applicable to cleaning and the removal of paint from CMU and brick substrates

Describe various methods of paint removal and cleaning, including advantages and disadvantages of each

Questions to Ask During Project Design

The following questions help to identify candidate coating cleaning or paint removal methods for the project:

– Does all coating have to be removed, or just loose coating?

– If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block?

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Questions to Ask During Project Design

(con’t)– Can roughening of the block or brick be

tolerated. If so, can it be heavy or only slight?

– Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)?

– Can airborne dust be tolerated?

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Industry Standards and Guides

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Industry Standards and Guides (SSPC)

• SSPC-SP13/NACE No. 6, Surface Preparation of Concrete– More of a Guide than a Standard – Frequently references other SSPC and ASTM Standards– Describes cleaning methods from air blow down and

vacuum cleaning to power tool cleaning, water jetting and abrasive blast cleaning

• Standard will be revised in a joint effort between the SSPC Surface Preparation Committee and the SSPC Commercial Coatings Committee

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Industry Standards and Guides (SSPC)

• SSPC-SP12/NACE No. 5, Surface Preparation and Cleaning of Metals by Water Jetting Prior to Recoating – replaced with:– SSPC-SP WJ-4/NACE WJ-4, Waterjet Cleaning of Metals –

Light Cleaning– SSPC-SP WJ-3/NACE WJ-3, Waterjet Cleaning of Metals –

Thorough Cleaning– SSPC-SP WJ-2/NACE WJ-2, Waterjet Cleaning of Metals –

Very Thorough Cleaning– SSPC-SP WJ-1/NACE WJ-1, Waterjet Cleaning of Metals –

Clean to Bare Substrate

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SSPC Visual Guides for Surface Cleanliness – Steel (not Concrete)• SSPC Visual Reference

Photographs are well established for the cleaning of steel, but none exist for the cleaning of concrete

• The SSPC Commercial Coatings Committee will be filling this void and developing reference photographs for the preparation of concrete-both cleanliness and roughness

Industry Standards and Guides (ICRI)

• ICRI Guideline No. 310.2 (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays

• Addresses water and detergent cleaning, acid etching, a variety of power tool methods, abrasive blast cleaning, and flame blasting

• ICRI 310.2 – 9 Concrete Surface Profile (CSP) Coupons

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Industry Standards and Guides (ASTM)

• ASTM D4258, Surface Cleaning Concrete for Coating– Broom cleaning, vacuum cleaning, air blast cleaning, water

cleaning, detergent cleaning, steam cleaning

• ASTM D4259, Abrading Concrete– Power tool, water blast, and wet/dry abrasive blast cleaning

• ASTM D4260, Liquid and Gelled Acid Etching of Concrete

• ASTM D4261, Surface Cleaning Concrete Masonry Units for Coating– Same as D4269 with the addition of mechanical tool

cleaning for the removal of mortar spatter and efflorescence

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Surface Preparation/Cleaning Methods in Standards/Guides

• Detergent Cleaning– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4258, ASTM D4261

• Air Blast Cleaning, Water Cleaning, Steam Cleaning, Vacuum Cleaning– SSPC-SP13/NACE 6– ASTM D4258, ASTM D4261

• Chemical Stripping – Effective method of paint removal, but not addressed in

the standards/guides11

Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Acid Etching

– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4260

• Flame Cleaning– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2

•  

• Power Grinding/Sanding– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2

– ASTM D4259

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Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Impact Power Tool Cleaning

– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

• Scarifying/Grinding/Scabbling/Milling– ICRI Guideline No. 310.2– ASTM D4259

• Water Cleaning/Water Jetting– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2

– ASTM D4259

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Surface Preparation/Cleaning Methods in Standards/Guides

(con’t)• Wet Abrasive Blast Cleaning

– SSPC-SP13/NACE No. 6– ASTM D4259

•  

• Dry Abrasive Blast Cleaning– SSPC-SP13/NACE No. 6– ICRI Guideline No. 310.2– ASTM D4259

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Candidate Paint Removal Methods for CMU/Brick

• Dry Abrasive Blast Cleaning• Wet Abrasive Blast Cleaning• Sodium Bicarbonate Blast Cleaning• Water Cleaning (Low Pressure <5,000 psi; High

Pressure 5000 -10,000 psi)• High Temperature Pressure Water Cleaning

(<5,000 psi)• Water Jetting (High Pressure 10,000 – 30,000 psi;

Ultra-High Pressure (>30,000 psi)• Power Tool Cleaning• Chemical Stripping

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Dry Abrasive Blast Cleaning

Abrasives propelledby compressed air

Very dusty – typicallyrequires containment system

Dry Abrasive Blast Cleaning

Boiler slag, copperslag, nickel slag,garnet, crushed glass,sponge, walnut shells, others

Dry Abrasive Blast Cleaning (con’t)

Difficult to selectivelyremove loose coating

Elastomeric coatings canbe difficult to removedue to bounce back ofthe abrasive

Potential for very heavyroughening of thesubstrate and damageto mortar joints, especially when trying to remove all coating

Wet Abrasive Blast Cleaning

Variation of dryabrasive blastcleaning

Water is mixed with the abrasiveto control dusting

Same potential toroughen the substrate as dryabrasive blast cleaning

Wet Abrasive Blast Cleaning (con’t)

Expendable abrasive,same as dry blastcleaning

Water is mixed withabrasive using:– Water collar– Special injection nozzle– Special equipment

that creates a slurry

Wet Abrasive Blast Cleaning (con’t)

Sodium Bicarbonate Blast Cleaning

Variation of wet or dryabrasive blast cleaning

Sodium bicarbonate (baking soda) is the abrasive

Larger particle size thanhousehold baking soda

Good for removing surface contamination,graffiti, and efflorescence

Sodium Bicarbonate Blast Cleaning – efflorescence

(wet)

Sodium Bicarbonate Blast Cleaning – fire restoration

(dry)

Water Cleaning Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Pressure categoriesdefined in – SSPC-SP WJ-4/NACE WJ-4– SSPC-SP WJ-3/NACE WJ-3– SSPC-SP WJ-2/NACE WJ-2– SSPC-SP WJ-1/NACE WJ-1

Despite the titles, the methods are suitable for CMU/brick

Water Cleaning (con’t) Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Will effectively removeloose coating

Zero degree rotatingtip improves efficiency

Can remove all coatinggiven ample dwell time

Generally 5.0 to 10.0gal/min

Water Cleaning (con’t) Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

Potential for using largeamount of water, especially for total coatingremoval

Increased dwell time for total removal can lead to water intrusion and wetting of interior surfaces

Water Cleaning (con’t) Low Pressure <5,000 psi

High Pressure 5,000 to 10,000 psi

When used for surface cleaning, operator discipline is required to assure the complete cleaning is achieved

High Temperature Low Pressure Water Cleaning

(<5,000 psi) Water temperature

250ºF and pressures <5,000 psi

High temperature improves cleaning efficiency when removing all coating

High temperature softens paint during removal

High Temperature Low Pressure Water Cleaning

(<5,000 psi) - con’t

Water Jetting High Pressure 10,000 to 30,000

psi Ultra -High Pressure >30,000 psi

Typically less water volume than low pressure cleaning methods

Efficiently removes existing coating, but can roughen substrate

Water Jetting (con’t)High Pressure 10,000 to

30,000 psi Ultra -High Pressure >30,000

psi Integral vacuum recovery system improves housekeeping and cleanup

Water Jetting (con’t) High Pressure 10,000 to

30,000 psi Ultra -High Pressure >30,000

psi

Power Tool Cleaning

Power sanding, power grinding, needle gunning, rotopeening

Vacuum shrouding available

Power Tool Cleaning

Sanding and grinding remove paint with less damage to substrate than impact methods

Power Tool Cleaning (con’t)

Power tool cleaning best used for localized removal

Sanding methods good for feathering

Chemical Stripping

Chemical stripping effectively removes existing paint

Biodegradable strippers are available that do not contain methylene chloride or caustic materials

Chemical Stripping – con’t

Stripper is first applied to the surface by brush, roller, or spray

Dwell time depends on coating type, temperature and thickness, but typically overnight

Chemical Stripping – con’t

Stripper and coating are removed by scraping, bucket and sponge, or pressure washing

Chemical Stripping – con’t

Depending on results, a second application may be necessary

Chemical Stripping

Second application essentially removes all coating

Original Project Design Questions

• Does all coating have to be removed, or just loose coating?

• If all coating must be removed, can small amounts still be permitted to remain in the porosity of the block?

• Can roughening of the block or brick be tolerated. If so, can it be heavy or only slight?

• Can large volumes of water be tolerated (environmentally and in terms of potential water intrusion into the substrate)?

• Can airborne dust be tolerated?

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Practical Use of Candidate Surface Preparation Methods

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1 – This table represents the practical application of the various methods when used under normal operations, but it is not absolute. For example, abrasive blast cleaning can partially remove existing coating from CMU or brick, and low pressure water (5k) can remove all coating, but they are not commonly used in these ways.2 – Sodium bicarbonate is best suited for surface cleaning rather than paint removal. It can be used wet or dry. If used dry, a large quantity of airborne dust is created. When used wet, little to no dust is generated.3 – Slight to heavy roughening may occur. Vacuum shrouding will significantly reduce the volume of water. Without vacuum shrouding, the volume is greater, but typically not as high as pressure washing at < 10,000 psi. 4 – Roughening created by power tool cleaning is dependent on the tool being used, ranging from slight to no roughening with power sanding to heavy roughening with power impact tools. 5 – A large volume of water is generated if the stripper is removed by pressure washing. Much less water is involved if removed by scraping and sponge/water to flush the surface, but this is only practical for small localized areas.

Paint Removal Methods1 Extent of Coating Removal Feasible

Substrate Roughening

Extent of Paint or Residue in

Porosity

Volume of Water Used

Quantity of Airborne Dust

Generated

Partial Total Slight to none

Heavy Slight Mod Mod Large Little Much

Dry abrasive blast x x x none x

Wet abrasive blast x x x x x

Sodium bicarb blast x2 x x2 x2 x2 x2

Pressure water (<10k) x x x x none

High temp water (<5k) x x x x x none

Water jetting (>10k) x x x3 x3 x x3 x3 none

Power tool cleaning x x 4 x 4 x none x

Chemical stripping x x x x5 x5 none

Productivity

Production rates for some of the methods can be found in:– Painting and Decorating Contractors of America (PDCA)

Estimating Guide, Volume 2, Rates and Tableswww.PDCA.org (314-514-7322)

– ICRI Guideline No. 310.2 (formerly 03732), Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlayswww.icri.org (847-827-0830)

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Additional Information• A paper associated with the information in this

webinar was published in Durability + Design Magazine – March/April 2011

• Sources of equipment and materials can be found in the Durability + Design on-line Painting Equipment and Supplies Buying Guide (under the Buying Guides tab on the home page)

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Removing Coatings and Cleaning

Masonry Substrates - Questions

Kenneth Trimber 412-788-1300,x204 ktrimber@kta.com