Electroless nickel plating is a process that provides corrosion and wear resistance in a single layer of deposit. Such layers are ideal for parts that are to be used in harsh environments and are likely to be subject to wear and/or corrosion.
Corrosion Resistance
The alloy deposit is made of pure nickel with phosphorus in solution. The phosphorus content in the coating gives it its corrosion resistance properties. High phosphorus Electroless Nickel deposits (10-13% P) have an amorphous structure. This means that the deposit is made of a random structure of nickel and phosphorus. This amorphous structure can block the diffusion paths that corrosion uses to reach the substrate metal. This is especially true for corrosive environments that are acidic or contain chlorides. Research has shown that increased phosphorus content in a nickel deposit greatly increases the corrosion resistance of the coating in these types of environments.
Hardness and Wear Resistance
Electroless nickel as-deposited has a hardness of approximately 550-600 HV. A post-plate heat treatment at around 400°C can, however, increase the hardness to over 900 HV. This makes it a suitable alternative to hard chrome where corrosion is not a major factor. However, the corrosion resistance is reduced by heat treatment.
Uniform Coverage on Complex Shapes
In contrast to many electroplated coatings, Electroless Nickel coats are uniformly thick on all internal surfaces including bores, blind holes and threads. For precision engineering components, with very tight dimensional tolerances on the internal features, this uniformity is a real plus point over other coating processes. For more on this, take a look at www.poeton.co.uk/surface-treatments/plating/electroless-nickel-plating/.
uk/surface-treatments/plating/electroless-nickel-plating/). Electroless Nickel Coating is worth getting right.
Base Metals and Suitable Environments
We can plate a wide variety of base metals including steel, stainless steel, aluminium and most of the copper alloys.
Specifying the Right Grade
If you tell your plating supplier what environment the part is going to be used in, what is the base material and whether wear or corrosion resistance is the major factor then the supplier can recommend the most suitable coating grade. They can then select the correct phosphorus level, coating thickness and whether a heat treatment is required to achieve the required hardness.
Matching the coating grade to the service conditions is key to obtaining the required performance.
