Electroless Nickel Plating MIL-C-26074, ASTM B733, AMS 2404
Electroless Nickel plating refers to the autocatalytic plating bath. That simply means that it plates through a chemical reduction of liquid metal ions plated to a base substrate. There is no electricity required for deposition. The base substrate reacts with the bath through the use of metal ions, reducing agents, complexing agents and bath stabilizers. It also requires a specific metal concentration, temperature and pH range. This also means that the base substrate will be plated at the same rate all over, barring any air or gas pockets. A sharp edge or corner will plate evenly without any extra buildup, unlike electrolytic plating. The bath requires constant monitoring and tight controls in order to maintain proper ratios.
The military specification associated with Electroless nickel is MIL-C-26074. The specification covers the different substrates to be coated. Class 1, 2, 3 and 4. Class 1 is, as plated, no additional heat-treating required, Class 2 is for parts that need to obtain a required hardness. Class 3 is for non-heat-treatable aluminum and beryllium alloys. Class 4 is for heat-treatable aluminum alloys, processed (baked) to improve nickel adhesion. This is only an overview of the specification. The specification covers all other requirements, testing, and sampling procedures that need to be followed for Electroless Nickel.
Electroless nickel has excellent corrosion resistance, wear and abrasion resistance, ductility, lubricity, solderability, electrical properties and hardness. As such, it is used in many different applications from food service, tools, computers, machinery and aerospace. The applications for this versatile coating are almost endless. Electroless nickel, after proper pretreatment, can also be plated on non-conductive surfaces.