When to Choose Electroless Nickel Plating

The right coating process for the right part. Here we highlight the key situations in which Electroless Nickel Plating is the preferred solution.

Table of Contents

Complex Internal Geometry

Many components feature blind holes, internal bores and recessed areas, such as threads. For components such as these, coating using electroplating is not suitable, because the current density of the electrical current, supplied by the anode(s), decreases with distance from the anode(s) and as a result does not reach the recessed areas of the component. As a result, coating in the recessed areas is poor. Electroless Nickel Plating, on the other hand, uses a chemical reduction process, and therefore coating occurs on all surfaces that are in contact with the bath, regardless of whether an electrode is brought into the area or not.

Tight Dimensional Tolerances

Many coating processes have a tendency to build up more on the edges of parts than elsewhere. Also, parts which have raised surfaces will sometimes end up with coating builds that are greater than required. When parts are to be assembled after coating and must fit within close tolerance, then it is necessary to plate to exact dimensions. For such parts, Electroless nickel plating is a good choice, since the coating builds up at a constant and predetermined rate, usually 12 to 25 micrometers per side.

Corrosion Resistance in Harsh Environments

A medium to high phosphorus content electroless nickel coating gives good corrosion resistance against exposure to salt spray, mild acids and other chemical process fluids. The coating forms a uniform layer of consistent thickness (typically 12 to 25 microns per side) that will provide a good, even corrosion resistant surface without the risk of localized patches of poor corrosion resistance that can form with a patchily applied electroplated coating.

Non-Conductive or Mixed Substrates

Electroless nickel can deposit onto aluminium and activated plastic surfaces. Also, components that consist of conductive and non-conductive parts can be coated with electroless nickel. This is an advantage over the electroplating process, which requires conductivity throughout the substrate.

RoHS and Chrome-Free Specifications

As with all surface treatments, when specifying a surface treatment to meet customer or supply chain specifications it is essential to check for any restricted or hazardous substances. Electroless nickel is a great alternative to other surface treatments such as electroplated chrome as it does not contain any hexavalent chromium, and is thus chrome-free. This makes it an ideal surface treatment for many industries including aerospace, defence and electronics. Furthermore, as electroless nickel does not contain any of the restricted hazardous substances as specified in the RoHS directive, it is a great alternative for companies and their customers looking for a surface treatment that is compliant with these regulations and does not require any exemption paperwork.

Match these five criteria to your part and the right choice becomes fairly straightforward.