Electroless nickel plating is a way of coating metal with nickel without using electricity. Instead, a chemical reaction makes a smooth, even layer of nickel form on the surface. This process is great for coating parts with complex shapes, holes or threads where normal electroplating can’t reach easily.
How It Works
Nickel is the fifth most common element, and it can be found in the crust and core of the Earth. In ENP, nickel ions in a solution are turned into solid nickel by a chemical such as sodium hypophosphite. Most ENP coatings contain between 2% and 14% phosphorus. The more phosphorus there is, the better the protection against corrosion, but the coating becomes slightly softer. The thickness of the coating is usually between 25 and 75 microns, although thicker layers are sometimes used for high-phosphorus coatings.
Why It’s Useful
Electroless nickel plating, such as the examples seen at https://www.poeton.co.uk/surface-treatments/plating/electroless-nickel-plating, gives excellent protection against rust and corrosion caused by things like salt water, oxygen and hydrogen sulphide. High-phosphorus ENP is especially good at this because it has no grain boundaries where corrosion can start. The coating also builds up evenly over the whole part – unlike electroplating, which can leave thin spots.
Performance and Durability
Even without heating, ENP is quite hard and wear-resistant. Heating it between 330°C and 360°C makes it harder but reduces corrosion protection. To get good adhesion, the metal surface must be cleaned well before plating. ENP is a cost-effective way to protect metal parts, extend their life and avoid corrosion problems on materials like carbon steel.
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