How Electroless Nickel Plating Works

Electroless nickel plating is an alternative to traditional electroplating techniques. In addition, it can plate various surfaces such as copper which are rather difficult to plate with the traditional processes. It is more cost effective as it does not require electric power.

Let’s Understand How Electroless Nickel Plating Works

Electroless nickel plating is an autocatalytic process in which a nickel alloy deposits by catalytic reduction onto the surface that requires plating; a catalytic reduction is a chemical reaction.

In this process, you immerse the surface requiring plating in a solution containing a nickel salt and reducing agents like sodium hypophosphite, which creates a nickel-phosphorous alloy, or sodium borohydride, which creates a nickel-boron alloy. The use of nickel-phosphorous alloy is more common. The reducing agent and the surface that needs plating to catalyze the ions in the solution and reduce these ions to nickel alloy atoms that then settle on the surface.

The deposited nickel alloy further serves as a catalyst for continuing the process, which is why we know the process as autocatalytic.

The plating solution also contains some other chemicals which stabilize the process. The choice of a reducing agent and its concentration in the solution is as important for effective plating as the concentration of nickel ions. You must manage the solution’s temperature, and pH as these can affect the plating quality.

The surface that needs plating determines how effective the plating will be. For the plating to adhere to the surface, the surface must be evenly smooth and free of dirt, oils, and other pollutants. Clean the surface with chemical cleansers, remove weld spatter, round out sharp edges, and ground out corroded areas of the surface.

Types of Electroless Nickel Plating

The type of plating depends upon the plating’s microstructure, and this microstructure depends upon the phosphorous amount in the nickel salt and reducing agent solution. The amount of phosphorous also affects the melting point and magnetic properties of the nickel alloy plating. A higher phosphorus percentage decreases the melting point, making soldering easier, but, at the same time, the plating’s magnetic effects diminish and vice versa.

Low-level solutions contain less than seven percent phosphorous. This creates a microcrystalline structure where each grain size is between two to six nanometers, and the plating is of uniform thickness even on inner surfaces. The deposited alloy has greater hardness. This plating is effective in resisting corrosion in alkaline environments.

For plating decorative items, electronic goods, and other industrial products, use a medium-level solution containing four to ten percent of phosphorous. The mix of amorphous and microcrystalline structures gives a brighter finish to the surfaces.

Solutions containing more than ten percent of phosphorous are high-level, and the microstructure of the plating is completely amorphous. Grain boundaries are sites at which corrosion is more likely to start. As there are no grain boundaries in an amorphous material, this type of plating offers higher corrosion resistance, especially in acidic environments.

If you need a more hardened surface and corrosion resistance is not a priority, you can increase the electroless nickel plating’s hardness with heat treatment. This treatment creates microcracks in the plating which increase the possibility of surface corrosion.

You can salvage worn products by electroless nickel plating. Apply several plating layers and if they exceed the original dimensions, remove some of the extra layers. The plating’s hardness makes this possible without damaging the product.

Benefits of Electroless Nickel Plating

The principal advantage of electroless nickel plating is that it facilitates the uniform plating of product surfaces and of shapes of varying complexities from tubes to spinnerets

The hardness of the electroless nickel plating reduces wear and extends the life of the plated products.

As this plating improves surface corrosion resistance, it is helpful in protecting surfaces from the corrosive effects of oxygen, carbon dioxide, various chemicals, and salt water. It is more economical to use electroless nickel plated products instead of expensive corrosion resistant alloys.

A variety of conductive and non-conductive surfaces can be electroless nickel plated. The finish of the plating surface can have a matte look or varying levels of brightness. For these reasons, it has become a popular plating method across a broad range of industries from Oil and Gas to Food Processing.