Aluminum/Electroless nickel••• a choice finish

By Keith Chadd & Tony George…

The process for electroless nickel plating on aluminum has advanced over the past decade from a rather complicated tech­nology to a very consis­tent, easily reproducible procedure. As a conse­quence of the continuous improvement in process­ing techniques, electro­less nickel is being relied upon more as a finish of choice by design engi­neers looking for light­weight, high strength materials in the manufac­ture of their products. While aluminum has a good strength-to-weight ratio and excellent machinability, electroless nickel can extend the ability of aluminum to function in applications where it could not be considered otherwise.

Friction, wear and appearance are

greatly enhanced by applying specific electroless nickel coatings.

For electronics applications, high

phosphorous electroless nickel

(TM 103) can provide non-magnetic

properties, corrosion resistance and

extended wear.

In the mold industry, electroless

nickel plays a big part in extending

the life of the mold by supplying the

surface with a hardness from 46-48

Rockwell C, and improved release

characteristics. Release characteris­tics can also be enhanced by impregnating Teflon into the nickel deposit (TM 117P) or applying a coating of teflon-nickel co-deposit (TM 117C). For food equipment manufacturers the advantages of a teflon co-deposit (TM 117C) is a light-weight part with corrosion resis­tance that is easy to clean.

In military applications, electroless nickel has been used for corrosion resistance in the manufacture of light-weight aluminum antennas as well as hydraulic rods.

Other opportunities have presented themselves in the last five years with the introduction of low phosphorous electro less nickel which has an as plated hardness of 57-61 Rockwell C.

This deposit can be deposited over high phosphorous nickel for applications where the part cannot be baked after plating to achieve hardness. This double deposit process gives high corrosion resis­tance to the part along with a high hardness close to that of hard chrome plating. When higher hard­ness is required, electroless nickel can be plated on aluminum which allows chrome plating to be applied to any critical surface with thickness­es up to .010 thick.

Techmetals provides coatings to the aerospace industry and helps in third developmental stages of new projects. One case in point is a cus­tomer request to replace hard coat anodize on an aluminum brake sleeve. 

The specification required that the

I.D: of the sleeve had to have a min­imum of .0015 per side thickness of hard chrome after final honing, which would require a heavy build-up. The problem with the specification was that it is very difficult to plate hard chrome on aluminum without damaging non-plated areas of the part.

Techmetals requested a specifica­tion change on the print to allow for Techmetal 103 to be applied to the

entire surface of the part which

would increase the corrosion resis­tance of the aluminum, and allow for the hard chrome to be applied with a higher degree of success and repeatability.

Techmetals commitment to contin­uous improvement in plating alu­minum with electroless nickel has opened a new door in engineering applications. Dedicated plating lines insure the quality of the products produced, and capacities have increased with the demand allowing parts to be plated as small as connectors to 10 foot long aluminum printing cylinders. There are going to be more applications for electroless nickel plated aluminum.