Alternate to Cadmium Plating-2

Electroless nickel effective thickness should be > 38 microns compared to 12 micron of Cadmium. This is a major problem for precision parts. Same apply for Xylen where to my best knowledge the thickness should be even larger. One more problem with Xylen is that it is not electrically conductive. Aluminum plating may be a problem when galling is an issue. Aluminum coated fasteners may gall with aluminum alloy parts.

I don't think electroless nickel and xylan will provide a self healing coating.

Alloyed with Zinc, Aluminium provides good electrolytic protection. How good it is on it's own, I'm not sure.

Why not electrozinc/aluminium? This will give a smooth coating if that is needed.

Zincalume galvanizing is probably cheapest where it can be used.

Not my specialty, but I do know that just up the road from us a small specialty coatings firm announced a 'new' process for them that was advertised as specifically to replace Cadmium-coated fasteners to be supplied to a couple of automotive sub-assembly plants in the area.

They don't have a website that I could find, but a press release about it noted that their coating system includes a chem/system bath for plating combined with a topcoat (possibly lubricant and torque enhancing) from and set up by this firm: MacDermid, which is probably your better contact point anyway.

Other than that, my military time included watching some in the field sample tests and reporting of the performance (which was quite good, actually) of something called "mineralized surface" treatments. I believe there was Zinc/Nickel involved and something about a "Siliconized" or "Polymerized" version, and those were with and without some kind of coating applied to them on top of that plating. I don't know of any level of strict tolerance in the mil thickness range that we would have had on our radar and com equipment deployment enclosures, so I doubt that was a consideration.

Thank you guys for your comments! The fasteners I am working on are relatively in largize (1"-3" dia and 1"-5" long) with UNC threads. So not high precision is required. The critical performance of the coating shall be good corrosion resistance and high temp resistance.

Electroless Nickel plating looks more promising from the perspective of performance vs cost. What do you think?

To my best knowledge electroless nickel has to be complete over the part/fastener. If the coating is mechanically damaged, thereby, exposing the bare metal it stops protecting the part and even worst it increase corrosion. As your part is a fastener and it can easily be damaged by tooling etc., I would recommend consulting with a corrosion engineer.

I would look into "white bronze". MFG name is Albaloy... I have used this extensively in rf and microwave applications (connectors). I believe the EU has disallowed Ni plating in the ROHS... Anyway, white bronze AKA Albaloy.

Is Ni plating banned in ROHS presently? I am not sure if bronze plating is ok, since the fastener's application is in oil and gas field and most enviroments are corrosive. Sour service is often too.

What about Black Oxide. It is a good general corrosion resistance treatment for steel with little dimensional change. It is also very reasonably priced.