.Electroplating

.CONTENTS Definition objective Electroplating process Disadvantages of electroplating Materials Technical information Hazards Typical products Electroless plating Immersion plating

When, in 1800,Alessandro Volta discovered how to make an electric battery , he unleashed the development of electro-chemistry. By 1806

Humphrey Davy, prolific inventor, has developed ways of plating metals from their salts and solutions – electro-plating.

The component (cathode) and the metalizing source material (anode) are submerged in the aqueous electrolyte where a direct electrical

current drives metal ions from the source to the component, creating a thin metal coating.

ELECTROPLATING

Some of the purposes for which articles are electroplated are:

•Appearance – colour, texture, reflectivity.•Protection – corrosion and wear

resistance.•Special surface properties.

•Engineering or mechanical properties.•Electrical conductivity.

.objective of ELECTROPLATING

.preparing of SURFACEThe cleaning or polishing operations may, therefore, require any one of the following steps:

1. Removal of all oil, grease or organic materials by immersing the parts in hot-alkaline solution, and lastly by rinsing in clean water.

2. Removal of surface irregularities, scale, and oxides by picking or by use of a file, abrasive wheel, or wire brush. The work piece must then be polished and buffed to ensure adhesion or to obtain the desired appearance.

.process of ELECTROPLATINGThe CuSO4 ionizes into water

CuSO4 --> Cu2+ + 2SO4 2-

The object is negatively charged > attracts Cu 2+and gives up electrons

The Copper atom will be deposited on the surface of the part being coated

Electro deposition

• Cathode made of copper or steel ; Anode made of Nickel

• Blue wire attached to the Cathode and negative pole of battery

• Red wire attached to the Anode and positive pole of battery

• The cell filled with an Electrolyte containing NiCl2

• For copper, brass and chromium, nickel is used as the base metal i.e. they need to be coated with nickel before coating the surface with other metals.

.preparation of ELECTROPLATING

Commonly Deposited Materials•Gold•Silver•Copper•Nickel•Tin•Solder (tin-lead alloy)•Brass•Cadmium•Palladium•Zinc

.MATERIAL

DESPITE OF ABOVE LISTED THERE ARE 63 OTHER TYPES OF MATERIALS.

Technical informationAlmost any metal can be electroplated. Polymers and other non-

electrically conductive materials must be first coated with an electrically conductive material.

Cleaning and surface preparation are essential.

The usual range of coating thickness is 1 to 50 microns, though thicknesses up to 1 mm are routine. Thicker coatings can generally be

produced more cheaply by other processes: thermal spraying, hot dipping or cladding.

The processing temperature is in the range 5-80 C.

Coat ability – the ease with which an electroplating can be applied – increases in this order :

Aluminum, mild steel, brass, copper.

Coatings working on a molecular level thin

coat If repeat it over and over again time

consuming and expensive The equipment cost for electroplating

is relatively high.

Uniformity Sometimes be lumpy and uneven

often grind and machine the parts

.disadvantage of ELECTROPLATING

Brittleness Electroplating a good coating of a

superior metal onto a lesser metal => coating often be brittle and easy to crack

Micro-crack may lead to the overall destruction of the electroplated layer electroplate multiple layers

.disadvantage of ELECTROPLATING

.Hazards Many electro-plating baths pose environmental and health hazards.

Some contain disagreeable chemicals-those with cyan-gens are downright nasty. Protection from chemical pollutants and toxic vapor

requires special precautions, as does the disposal of the plating medium.

Cadmium is toxic, and now banded as plating in many European countries.

Alternatives to chromium plating, one of the more unpleasant of processes, are sought but not yet found.

Nickel can cause allergies and should be kept away from skin contact.

.ALBUM

Types and typical products.Aluminum

Aluminum electro-plating can substitute for hot dipped aluminum, but is infrequently used.

BrassBrass lamps and trays, low cost trim, interior automotive hardware, tubular

furniture, household goods, toys, casket hardware, novelties, promote adhesion of rubber to steel.

BronzeBronze inexpensive jewellery, door plates, hardware, trophies, handbag

frames, undercoat for nickel and chromium, bearing surfaces, tableware, household fixtures.

CobaltMirrors, reflectors, applications where high hardness is required.

Co-NiPermanent magnet coating on memory drums in digital computers.

CopperWire coatings, thermally conductive coatings on cooking utensils, electro-forming.

GoldGold pen points, jewellery, watch and vanity cases, trophies, novelties, springs,

electronic parts, name plates, musical instruments.

NickelNickel base for thin chromium electroplates, trim for automobiles, business

machines and customer goods.

RhodiumCostume jewellery, emblems, musical instruments, medical and surgical parts,

electrical contacts, reflectors and mirrors.

SilverSilver tableware, musical instruments, surgical instruments, bearings,

candlesticks.

TinTin food and beverage containers, hardware, electronic parts, bearings, copper

wire.

Types and typical products.

Tin-NickelCooking utensils, surgical instruments, watch parts, chemical pumps,

valves and flow control devices.

Tin-ZincTin-Zinc radio and television parts, cable connectors.

ZincZinc appliances and automotive parts, finishing small parts(bolts, nuts,

rivets, washers, nails, hinges), telephone exchange equipment.

Types and typical products.

.amazing factThe basic problem in attempting

to electroplate onto plastics substrates is, of course, that

they are electrically non-conductive and cannot be

immersed in a plating solution and coated in the way that metal objects can. Some

method was therefore needed whereby a conductive film could be deposited onto the plastics surface to provide the basis for

subsequent electro deposition. It was, of course, vital that this surface layer, in addition to

being electrically conductive, should adhere well to the

substrate if the final coating system was to show good

adhesion

ABS

If you are trying to get a "mirrored finish" on printed parts, you could Vacuum Metalize the parts instead. It is cheaper, you don't need it to be made out of a special ABS grade, and the clear coat finish could then be tinted to look like gold, mirrored red, mirrored green etc.. Like Christmas tree ornaments. I don't know if PLA could be vacuum metalized, it needs to resist a high vacuum, take a static charge, and not outgas too much in

the VM chamber.

.amazing SUB-PROCESS

vacuum metalizing is what you are looking for. This is quite an interesting procedure. Basically the piece you want finished is put into a vacuum

chamber with your chosen metallic finish. The finish that is being applied gets heated then it starts to evaporate. This metal once vaporized molds

on the product as a thin metallic film.

The part that is being coated is also being rotated in the chamber. This provides for uniformity with coating.

This vacuum metalizing can be done on many different products. Some of these are glass, plastic, metal, ceramic and paper. Really this can be done on just about anything. Any size can be done as well yet some

larger items may have to be broken down for the process. There are also many metals that can be used for the coating

.amazing SUB-PROCESS

ELECTROLESS PLATING-

IMMERSION PLATING-

Other competing processes : solvent and water based painting; mechanical polishing; electro-polishing; anodizing and vapor

metalizing.

.other PLATING PROCESS

In Electroless plating (also known as autocatalytic plating) metals are deposited on to the surface of a part without using an external source of electricity. A standard electroless plating

solution contains the following : metal salts (as source metals), a reducer which is an electron-donor to the metal ion, a catalyst

to accelerate the reaction allowing metal deposition, a complexing/chelating agent that allows the metal to stay in

solution.The metallic ions in the plating solution are reduced to

superfine metallic particles and deposit evenly on the srface of the part,independent of the part geometry.The even plating

thickness is a major advantage in this type of plating over the conventional electroplating.

.ELECTROLESS PLATING

Advantages include:

1. Does not use electrical power.2. Even coating on parts surface can be achieved.3. Palatable on non-conducting materials such as plastics.4. No sophisticated jigs or racks are required.5. Complex filtration method is not required.6. Solder ability.7. Good wear.8. Corrosion resistance9. Matte, Semi Bright or Bright finishes can be obtained.10.Usually hydrogen is released in this process.

Disadvantages include:

11.Lifespan of chemicals is limited.12.Waste treatment cost is high due to the speedy chemical renewal.

.dis/adv. of ELECTROLESS PLATING

Immersion plating is a process similar to electroless plating.In this process,the base metal from the workpiece is displaced with another

metal iom in the plating solution.The metal ions in the plating solution have a lower oxidation potental than the displaced metal.This

process,like electroless plating,uses chemical reactions to apply a metal finish to the substrate.Immersion plating differs from electroless plating in that the reducing agent is the base metal of the workpiece and not a

chemical additive,as is the case in electroless plating.The thickness of deposits obtained in immersion plating is limited

because deposition stops when the entire surface of the base metal is coated.

.IMMERSION PLATING

.dis/adv. of IMMERSION PLATINGAdvantages include:

1. Does not use electrical power.2. Even coating on parts surface can be achieved.3. No sophisticated jigs or racks are required.4. The process can plate recesses and blind holes with stable thickness.5. Chemical replenishment can be monitored automatically.6. Complex filtration method is not required7. Matte, Semi Bright or Bright finishes can be obtained.

Disadvantages include:

8. Life span of chemicals is limited.9. Layer of plating is very thin as compare to any other process .10.Waste treatment cost is high due to the speedy chemical renewal.

.reference VIJAYLAKSHMI ELECTROPLATER , HBR LAYOUT

POOJA INDUSTRIES , PEENYA

.thank you