Chemical nickel

niquel

 

 

 

 

 

Electroless Nickel plating is an industrial process in which a nickel-phosphorus alloy is deposited without an external electrical current.

This process provides exceptional technical solutions due to its unbeatable hardness qualities, wear, friction, abrasion and corrosion resistance.

It is used instead of conventional electrolytic treatments to coat complicated, hollow or irregular workpieces containing regions that cannot be accessed by an electrical current.

Its most important characteristics are:

a) Uniform thickness.

It provides identical corrosion protection in all regions of the workpiece.

It differs from electrolytic coating in that the latter deposits very different thicknesses at one point of the workpiece and another, causing corrosion to begin in regions where the deposits are thinnest.

b) Some properties can be varied in function of the heat treatments performed.

The influence of prior heat treatments is due to the fact that Electroless Nickel deposition forms an alloy whose molecular structure is temperature dependent. One of the heat treatments most typically applied is that used to increase the hardness of the coating, which can reach 1100 Vickers.

Electroless Nickel coatings can be applied to most metals, such as cast irons, carbon steels and their alloys, stainless steels, aluminium, copper, cobalt, monel, nickel and its alloys, gold, platinum and uranium, and even to some thermally stable plastics, such as bakelite, melamine, ceramics and glass, provided a powerful catalyst can be applied to their surface.

Zinc, cadmium, lead, bismuth, antimony and tin cannot be coated directly as these metals prevent nickel deposition, thus meaning that they must be coated with another metal (e.g. electrolytic copper) before nickel plating.

Electroless Nickel plating competes with Hard Chrome plating because it does not require subsequent rectification. It can also be used to form an underlayer, in other words an initial layer of nickel followed by one of chromium, with this combination providing greater thickness consistency whilst maintaining the exceptional surface qualities of Hard Chrome plating.

It can be used as an underlayer in the case of:

- Gold
- Cadmium-, tin-, silver-, gold-plated aluminium, etc. thereby favouring subsequent welding.

Its use also provides economic advantages, such as:

- Weight savings, by replacing a heavy alloy with a lighter, nickel-plated alloy. This has allowed the car industry to use nickel-plated aluminium alloys to make significant savings in weight and also results in highly advantageous surface properties in terms of hardness, friction, wear resistance, etc.
- Production costs can also be reduced by using a standard nickel-plated material rather than a heavier one, for example in the electrical industry, which has replaced copper with tin-plated aluminium thanks to a prior coating with Electroless Nickel.

A SHORT HISTORY OF ELECTROLESS NICKEL PLATING

The research and development department of the Central American Transportation Company decided to study the problem of how to protect the interior of tankers used to transport chemicals without generating impurities as a result of corrosion.

The prohibitive cost of resistant "linings" or electrochemical coatings led to the idea of using Electroless Nickel plating to overcome the drawbacks of its electrical counterpart (poor penetration, point defects, joints, porosity, auxiliary anodes, etc.).

Between 1947 and 1952, a team of chemists, metallurgists, physicists and engineers managed to optimise an industrial method covering all stages from surface preparation to plating bath regeneration. This method subsequently became known as KANIGEN (KAtalitic NIckel GENeration). This method has spread rapidly since the first pilot plant in the USA, owned and run by C.A.T. Co., began operating in 1952. The process reached Europe in 1955 - 56 via the Societé de Révetement Chimique (S.E.U.R.E.C.) in Paris, and there are currently workshops in the USA, France, Switzerland, the UK, Belgium, Japan, Australia, Spain, Germany, Yugoslavia, Italy and Hungary.

Tecnocrom Industrial acquired the method in 1965 as the first licensee of S.E.U.R.E.C. in Spain, and the methodology has since been improved and continues to be applied for various specific tasks.

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