Electroless Nickel Plating ....

In contrast to conventional electroplating, Electroless Nickel Plating (ENP) is produced by a chemical process alone, without the use of an electric current. This results in a highly uniform, controllable deposit over the whole workpiece, even down long bores and overcomes one of the main weaknesses of electrolytic plating. The coating is actually a nickel-phosphorous alloy which gives a surface similar to chromium plating in appearance with a unique combination of hardness and wear resistance combined with excellent corrosion resistance and chemical resistance.

While there is no theoretical limit to the coating thickness, (very simply stated, thickness is a function of immersion time) there are certainly practical and commercial considerations. Coating thickness is normaly in the range 2 to 50 microns, and usually 10 to 12 microns is sufficient. Thickness can be controlled very accurately, Eliminating the need for post plating machining operations. As with any plating process dimensional growth needs to be taken into account but, unlike anodising, the growth is double the film thickness on diameter. Masking can be done to protect surface but this can add substantial cost. Since coatings follow the profile of the underlying surface, that profile will be reproduced, including faults, at the newly formed surface.

Nickel-Boron alloys can also be plated on for more specialist applications and Electroless Nickel Plating containing fine particulate PTFE can be applied to impart coatings with low coefficients of friction.

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PROPERTIES

HARDNESS
The as-plated film has a hardness of 500-600 Vickers (45 – 54 Rockwell C Equivalence). This can be increased by heat treatment up to, for suitable substrates, around 1000 Vickers.

CORROSION RESISTANCE
Similar to high grade stainless steel

ABRASION/WEAR RESISTANCE
The Electroless Nickel Plating surface has a natural lubricity which, in combination with the hardness, makes it ideal for applications where wear and abrasion resistance are essential. It is best used in combination with dissimilar surfaces e.g. chromium or stainless steel. Sliding contact between ENP surfaces should be avoided.

SOLDERABILITY
Electroless Nickel Plating has excellent solderability and is used to confer this property on other metals. For the best results the film should be relatively fresh and an appropriate flux should be used.

BRAZING AND WELDING
Numerous substrates can be brazed if they are given an Electroless Nickel Plating surface. Welding is not recommended, as the phosphorous tends to migrate toward grain boundaries, causing cracking.

SUBSTRATE MATERIALS
Many metals can be Electroless Nickel Plating plated including iron and steel, aluminium alloys, brass, bronze, copper, stainless steel and nickel itself. It is also possible to plate titanium and magnesium and processes have been developed to plate plastics. There is usually no difficulty associated with Electroless Nickel Plating on castings.

Electroless Nickel Plating - APPLICATIONS

Aerospace Protection of hydraulic control systems. Refurbishment/recovery of worn or incorrectly machined components.

Electrical/Electronics Protection of components e.g. Capacitors. Imparts solderability.
Energy Industry To impart chemical and wear resistance to oil & gas industry equipment. To impart wear resistance to coalfield cutting tools without risk of sparking.

General Engineering A wide range of applications employing the unique properties of the system. For example: wear resistance in plastics and textile handling equipment; Corrosion resistance in chemical handling plant, appearance and wear; Resistance in automotive applications etc.