The term “nickel plated” usually refers to the electroplating of nickel metal onto the surface of an item via the traditional 'electrolytic' method.<[etk]>
The electrolytic method involves electrical current passing through a solution and in the process transferring metal from an ‘anode’ to the job, or ‘cathode’.
Electro-less Nickel (E-Ni) plating results in a nickel coating via a method that does not involve electrical current.
In engineering environments electro-less nickel plating is a process that has many advantages over ‘electrolytically’ applied nickel.
The coating can be used in many fields where a hard, corrosion-resistant finish is required. A major advantage of the process is that it is possible to coat the whole surface of an item evenly, including internals, unlike electrolytic processes which have difficulty depositing into recessed and internal areas and can result in excessive build-ups of plating on points and corners.
Examples of items that can benefit from electro-less nickel coatings are injection moulding tools and dies, pumps and valves, shafts, rollers, and other general machinery.
The E-Ni process can provide significant savings when comparing to a process such as hard chrome on a complex shape, as the article can be machined to shape prior to coating (with an allowance for plating thickness) and should not require any post machining to regain the required precise dimensions (hard chrome usually necessitates machining back to tolerances and shape).
To create an internal coating by electrolytic methods requires the use of complex anode arrangements that are often costly to produce and set-up. It is possible to achieve deposits of E-Ni into internal areas where it would be impossible to use electrolytic methods.
For example, consider an injection-molding die machined to specification with allowance for several microns E-Ni.
The die is plated and put straight to work, meaning no post plating machining is required. The resulting surface has significantly more lubricity than the original steel, so parts release more efficiently.
The die is protected from corrosion when stored resulting in minimal maintenance costs. The die is also protected when in production and subject to water cooling, resulting in less corrosion problems.
Other advantages of electro-less nickel include lubricity (able to slide over other metal surfaces without galling), hardness (a variety of solutions types give a variety of as plated hardnesses), corrosion and abrasion resistance, and resistance to a wide range of chemicals.
It also features good mould release, while additives such as Teflon or silicon carbide can be included into the deposit to further increase properties such as lubricity and wear resistance.
Parts can also be manufactured from mild steel and coated with electro-less nickel to provide similar performance to stainless steel at a much lower cost.
*Amanda Wood is MD of A Class Metal Finishers .