.Electroplating
.CONTENTS Definition
objective Electroplating process Disadvantages of electroplating Materials Technical information Hazards Typical products Electroless plating Immersion plating
ELECTROPLATING 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.
.objective of 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.
.preparing of SURFACE The 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 ELECTROPLATING The CuSO4 ionizes into water CuSO4 --> Cu2+ + 2SO4 2The 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
.preparation of ELECTROPLATING •
• • • •
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.
.MATERIAL Commonly Deposited Materials •Gold •Silver •Copper •Nickel •Tin •Solder (tin-lead alloy) •Brass •Cadmium •Palladium •Zinc
DESPITE OF ABOVE LISTED THERE ARE 63 OTHER TYPES OF MATERIALS.
Technical information Almost any metal can be electroplated. Polymers and other nonelectrically 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.
.disadvantage of ELECTROPLATING 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
.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. Brass Brass lamps and trays, low cost trim, interior automotive hardware, tubular furniture, household goods, toys, casket hardware, novelties, promote adhesion of rubber to steel. Bronze Bronze inexpensive jewellery, door plates, hardware, trophies, handbag frames, undercoat for nickel and chromium, bearing surfaces, tableware, household fixtures. Cobalt Mirrors, reflectors, applications where high hardness is required.
Co-Ni Permanent magnet coating on memory drums in digital computers.
Types and typical products. Copper Wire coatings, thermally conductive coatings on cooking utensils, electro-forming. Gold Gold pen points, jewellery, watch and vanity cases, trophies, novelties, springs, electronic parts, name plates, musical instruments. Nickel Nickel base for thin chromium electroplates, trim for automobiles, business machines and customer goods. Rhodium Costume jewellery, emblems, musical instruments, medical and surgical parts, electrical contacts, reflectors and mirrors. Silver Silver tableware, musical instruments, surgical instruments, bearings, candlesticks. Tin Tin food and beverage containers, hardware, electronic parts, bearings, copper wire.
Types and typical products. Tin-Nickel Cooking utensils, surgical instruments, watch parts, chemical pumps, valves and flow control devices. Tin-Zinc Tin-Zinc radio and television parts, cable connectors.
Zinc Zinc appliances and automotive parts, finishing small parts(bolts, nuts, rivets, washers, nails, hinges), telephone exchange equipment.
.amazing fact
ABS
The 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
.amazing SUB-PROCESS 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
.other PLATING PROCESS ELECTROLESS PLATINGIMMERSION PLATING-
Other competing processes : solvent and water based painting; mechanical polishing; electro-polishing; anodizing and vapor metalizing.
.ELECTROLESS PLATING 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.
.dis/adv. of 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 resistance 9. Matte, Semi Bright or Bright finishes can be obtained. 10. Usually hydrogen is released in this process.
Disadvantages include: 1. Lifespan of chemicals is limited. 2. Waste treatment cost is high due to the speedy chemical renewal.
.IMMERSION 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.
.dis/adv. of IMMERSION PLATING Advantages include: 1. 2. 3. 4. 5. 6. 7.
Does not use electrical power. Even coating on parts surface can be achieved. No sophisticated jigs or racks are required. The process can plate recesses and blind holes with stable thickness. Chemical replenishment can be monitored automatically. Complex filtration method is not required Matte, Semi Bright or Bright finishes can be obtained.
Disadvantages include: 1. Life span of chemicals is limited. 2. Layer of plating is very thin as compare to any other process . 3. Waste treatment cost is high due to the speedy chemical renewal.
.reference VIJAYLAKSHMI ELECTROPLATER , HBR LAYOUT POOJA INDUSTRIES , PEENYA
.thank you
