Here at us, we spend our days electroless nickel plating components for a variety of applications including aerospace, electrical/electronics, the energy industry, and general engineering.
Properties of electroless nickel coatings
Electroless nickel coatings produce very tough, abrasion and corrosion resistant surfaces, which can be further hardened with heat treatment. The hardness of the plated surface can also be increased by decreasing the phosphorus content of the coating, usually to around 2%.
They also have a good natural corrosion and chemical resistance. These properties can also be maximised by increasing the phosphorus content of the coating, usually to 10% or above.
Electroless nickel and phosphorous levels
The chemistry of electroless nickel plating solutions can be altered to give the plated coating different properties, for example, a medium phosphorus coating, a low phosphorous coating and a high phosphorus coating.
Medium Phosphorous electroless nickel coating
Electroless nickel coatings with medium phosphorous content are the most commonly used and applied electroless nickel coatings. They generally have a phosphorous content of 6-9% and a VPN of roughly 500. However, this can be increased further with heat treatment. The coating tends to be bright, with a normal plating thickness range of 3-50 microns. Medium phosphorous electroless nickel coatings are very stable and reliable with fast plating rates.
Low phosphorous electroless nickel coating
Low phosphorous electroless nickel coatings contain less than 3% phosphorous and are very hard. With the appropriate heat treatment, a low phosphorus coating can be in the region of 1000 Vpn. The normal plating thickness of this type of coating is in the region of 10-25 microns and is grey/silver in colour.
High phosphorous electroless nickel coating
Electroless nickel coatings with high phosphorous contents typically have very high levels of corrosion and chemical resistance. High phosphorous coatings are non-magnetic, silver/grey in colour and have a normal thickness range of 25-75 microns. Plating rates are typically slow and the plating solution tends to have a short life.