ELECTROPLATING PLANT

Electroplating is a reliable and fast deposition process through which an adherent metallic coating is obtained on a vast variety of metal surfaces. This process of applying protective & decorative coatings has so greatly advanced that properties, dimensions of coat and coating rates can be strictly controlled. Tin, Silver, Rhodium, Platinum, Palladium Zinc, Iridium, Lead, Gold, Nickel, Chromium, Copper, Brass & aluminum are the most used coatings on variety of metal substrates. Any metal & metal alloy product produced in industries can be provided with suitable protective/decorative coating with the use of proper electrolyte bath, electroplating equipments & accessories, anodes/cathodes and control instruments while discussing adherent coating, it is advisable to understand that electroformed adherent coating is obtained exclusively by electroplating while electro deposition coatings may include electroless plating and immersion processes too. It is remarkable that practical & technological phases of electroplating matured even before Faraday’s laws of electrolysis was pronounced.

Until World War-I, electroplating was considered an art. The then electroplaters did not bother to know even the fundamentals of electricity and chemical reactions that took place in the electroplating process. At that time, appearance & appeal of the electroplated surfaces were considered more important than the physical & chemical properties of the coat. It was around World War – II that close tolerances & rigidly specified properties converted electroplating into a technology from its art – status.

Today, electroplating is an advanced science & engineering due to advancements in metallurgy, physical/electro chemistry. Suitable equipments, measuring & control instruments/devices have been developed for the purpose. The use of direct current as the source of energy for electroplating process and thermocouples for controlling temperature-rise in the process, has made electroplating highly reliable. The chemical industry has made available well-suited chemicals, salts, oxides, acids and other constituents for use as a standard bath formulation for every specific metal coating. Electronics, automobiles and various other industries have demands for electroplated products.

Electroplating is a surface treatment. The material being coated is made the cathode and placed in the electroplating solution or bath. Baths are often aqueous solutions of their salts. Aluminum is an exception which is plated on a semi commercial scale from organic electrolytes. Some refractory materials (e.g. niobium, tantalum etc.) can also be deposited from fused salts as coherent plates. The coat-thickness, deposited by electroplating, varies widely (from 0.025 um for decorative gold/plating to 25-50 um far standard Ni-Cr coats on automotive components). The coating thickness can be obtained upto 1mm in certain cases by electroplating deposition process.

The properties conferred by electroplated coatings include (i) imporved corrosion resistance, (ii) Wear resistance, (iii) hardness, (iv) solder ability, (v) Good appearance, (vi) frictional characteristics, (vii) specific electrical properties, etc.

Applications:-

The main reasons for electroplating products depend on their applications. Hence, electroplating can have the following applications.

1. Decorative appearance,

2. Protection against rust, stain, corrosion and wear,

3. To create special surface properties,

4. To develop engineering & mechanical properties in the products.

Decorative Appearance:-

Chromium coating is mostly used for decorative purposes. Chrome plated items have an aesthetic appeal. Before enacting the thin layer of final chromium plate, the product is given an under electrodeposited coat of copper or nickel or both.

Other metals used for decorative electroplate are:- gold, platinum, rhodium, brass, bronze, nickel, copper, silver and lead, tin etc. Automotive & aircraft parts, refrigerator parts, electrical appliances, sanitary fittings, furnitures, fire arms, artificial jewellery, etc. bear decorative coatings.

Protective coatings:-

Certain structural metals are prone to rusting, staining, pitting by corrosion etc. Steel is an important example. The structures exposed to atmosphere and other corroding environments soon get adversely affected. Thus, they lose the effective life and can fail prematurely. Such cases suggest coating their surfces with any other material that can project the basis metal (e.g. steel) galvanically. On coated metals, the corrosion occurs sacrificingly. Zinc or cadmium is found suitable coating materials in such cases. These metals can be coated by electroplating as well as other non-electic processes.

Tin plating also is used on steel for the same reason.

Special Surface Effects:-

Rhodium electroplating is used for better reflectance, silver for improved electrical properties and gold for good electrical contact. Gold cadmium & lead – tin alloy are electroplated for achieving good solderability. Modern electronics industry used electroplating for great many special effects.

Need for Standardization:-

Now-a-days Electroplating is an important industrial process which is provided on metal products for protective & decorative finishes. Also non-metallic materials like plastics are electroplated for certain necessary benefits.

Electroplating is employed for various advantages like corrosion-resistance, wear-resistance, case of soldering food preservation, re-building of the worn-out components and appealing finishes.

In order to obtain good deposits by electroplating, standard procedures are practiced in a well-equipped plant. Pretreatments such as buffing, polishing degreasing and cleaning/drying ensure good plating quality.

Electroplating processes are so higly standardized that the final products can be accurately tested & certified to hold the ordered quality. The basis metals being electroplated should be free from scales & non-metallic inclusions like slags, refractories, deep-pits, blisters, cracks, porosity & burrs. Non-metallic inclusions must be avoided as these are non-conductor of electricity and hence, cause discontinuity in the coating.