In electroplating, a metal-containing ion is provided with electrons to build a non-ionic coating on a substrate. Usually, a chemical solution is taken with the metal in the ionic form. Then there is an anode which may be made up of the metal that is being plated. The anode can also be insoluble made up of substances like carbon, platinum, lead, titanium, or steel. Then there will be a cathode where the electrons are supplied to form a film of non-ionic metal.
In electroplating service a thin layer of metal is deposited electrolytically on a base metal to improve or change its appearance. Electroplating is done using a liquid solution called electrolyte.
Electroless Plating
Electroless plating is also known as auto-catalytic or chemical plating. The method is the non-galvanic plating method where simultaneously different reactions take place in an aqueous solution without the use of external electrical power. The reaction is achieved when hydrogen is given out by a reducing agent. Usually, sodium hypophosphite is oxidized producing a negative charge on the part surface.
The most common method of electroless plating is nickel electroless plating. In electroless nickel plating, the deposits are of uniform thickness even on parts of complex shape provided the part is properly designed. There are no issues with the current density. The thickness of the plating depends on the time the part remains in the tank. Electroless nickel plating is a process of chemical reduction which depends on catalytic reduction process of nickel ions in an aqueous solution and the resultant deposition of nickel metal without the use of electrical energy.
Areas of application of Electroless Nickel
Electroless nickel is used in a lot of applications due to its unique properties of excellent corrosion resistance along with uniform coating and high wear resistance. Some of the fields in which it is used include:
- Food and pharmaceutical: chocolate molds, capsule machinery dies, food processing machinery components and more
- Textiles: Machine parts, printing cylinders, spinnerets, threaded guides and more
- Aviation and Aerospace: Rocket and satellite components, rams pistons, valves components, etc.
- Automotive: heat sinks, gears, shock absorbers, cylinders, brake pistons, etc.
- Plastics: Molds and dies for injecting and low and blow molding of plastics, extruders, machine part rollers, etc.
- Chemical processing: Filter units, heat exchangers, pump housing and impellers, mixing blades, etc.
- Oil and Gas: Valve components such as gates, balls, plugs etc.
The solderability of electroless nickel is considered to be very good and they recommend using low phos for best solderability and longest shelf life. Hence it is used in a lot of applications in different fields from electronic to mechanical and others.
Summary
In electroless plating of nickel, the deposits are considered to be uniform even on parts with complex designs.
