Electroless Nickel Plating – Process , Advantages and Applications

What is Electroless Nickel Plating :

The process of adding an electroless nickel plating to a metal surface is an autocatalytic chemical reduction. This means that instead of using an outside source of electricity like in the similar electroplating process, the electroless nickel plating process uses a chemical bath to deposit a nickel / phosphorous layer onto the metallic surface. A surface coated in electroless nickel can even be used on non-conductive surfaces which allows for plating of a wider variety of base materials. This electroless process greatly improves the objects resistance to galling and leaves a predictable, uniform nickel coating for high-precision parts, which can be applied to both ferrous and non-ferrous surfaces of any geometry or intricate shape.

Electroless nickel plating is an auto-catalytic reaction used to deposit a coating of nickel on a substrate. Unlike electroplating, it is not necessary to pass an electric current through the solution to form a deposit. This plating technique prevents corrosion and wear. Electroless nickel plating techniques can also be used to manufacture composite coatings by suspending powder in the bath. Electroless nickel plating has several advantages compared to electroplating. EN plating is free from flux-density and power supply issues and provides an even deposit regardless of workpiece geometry. With the proper pre-plate catalyst, EN plating can deposit on non-conductive surfaces.

EN Plating Steps Process

First and foremost, the surface undergoes a pretreatment process where it is cleaned with a series of chemicals to remove greases and oils. Thorough cleaning is essential in preapring the component for proper plating. Each component is meticulously cleaned based on the surface material.
Once cleaned, the substrate is activated with an acid etch or proprietary solution, preparing the surface for a deposit of nickel-phosphorus.
After the plating has been completed the electroless nickel process renders the component more resistant to corrosion and friction.
Electro-Coatings uses it’s close to 70 years of experience and these Electroplating techniques to manufacture unique composite coatings that provide more application specific advantages.

Electroless Nickel Plating Thicknesses

Electroless nickel plating can be deposited at a rate of 5 microns per hour all the way up to 25 microns per hour. Since it is a continuous process that builds on itself the thickness of the coating is essentially limitless. As thickness increases however, minute imperfections become more apparent.

Advantages include:

Does not use electrical power.
Even coating on parts surface can be achieved.
No sophisticated jigs or racks are required.
There is flexibility in plating volume and thickness.
The process can plate recesses and blind holes with stable thickness.
Chemical replenishment can be monitored automatically.
Complex filtration method is not required
Matte, semi-bright or bright finishes can be obtained.

Disadvantages include:

Lifespan of chemicals is limited.
Waste treatment cost is high due to the speedy chemical renewal.
Porous nature of electroless plating leads to inferior material structure compared to electrolytic processes.

Applications

It is commonly used in engineering coating applications where wear resistance, hardness and corrosion protection are required. Applications include oilfield valves, rotors, drive shafts, paper handling equipment, fuel rails, optical surfaces for diamond turning, door knobs, kitchen utensils, bathroom fixtures, electrical/mechanical tools and office equipment. It is also commonly used as a coating in electronics printed circuit board manufacturing, typically with an overlay of gold to prevent corrosion. This process is known as electroless nickel immersion gold.

Due to the high hardness of the coating, it can be used to salvage worn parts. Coatings of 25 to 100 micrometers can be applied and machined back to the final dimensions. Its uniform deposition profile means it can be applied to complex components not readily suited to other hard-wearing coatings like hard chromium.