Electroless nickel plating

Electroless Nickel Plating (ENP) is the deposit of a nickel-alloy coating by chemical reduction – without the electric current that’s used in electroplating processes.

The majority of ENP for engineering purposes is a nickel phosphorus deposit containing 2 to 14% phosphorus.

The higher the phosphorus content the greater the corrosion resistance, however the compromise on increased phosphorus content is a decrease in hardness.

ENP is deposited by reducing nickel ions to metallic nickel with a chemical reducing agent such as sodium hydrophosphite. Thickness of 25-75m is common, high phosphorus ENP can edge above 75m although this does start to push the limits of ENP.

The benefits of electroless nickel plating

ENP offers excellent corrosion resistance to common corrodents such as salt water, carbon dioxide, oxygen and hydrogen sulphide.

High phosphorus deposits of ENP (10-14% phos) is also amorphous, which means that there are no grain or phase boundaries to create initiation sites for corrosion.

The uniformity of ENP versus electrolytic deposits is also advantageous, creating a uniformly thick coating across the whole substrate; even in slots, holes and inside walls of tubing.

Without heat treatment corrosion resistant high phosphorus ENP still provides good hardness and wear resistance properties.

ENP offers a cost-effective solution for applications subject to conditions where wear and corrosion are factors; extending service life and providing a lower cost alternative to corrosion resistant alloys, particularly where carbon steel suffers localised corrosion; flange attack or weld corrosion.