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Stripping Cadmium Plating from Fasteners

 

I am restoring a mid-fifties American car. Many of the bolts used by the manufacturer are National Fine thread, with a natural (oiled?) finish.

While I can easily find cad or zinc plated NF nuts & bolts, it seems impossible to obtain a match for the existing natural finish ones. It has been suggested that I can remove the plating using muriatic acid [affil links] to get the dark natural finish I am looking for.

Is this possible on a do-it-yourself basis? If so, can you provide some rules-of-thumb as to time to remove plating, suggested neutralizing solution, etc. Is there any risk of altering the strength properties of the fasteners by removing the plating?

Ken Stone
- Calgary, Alberta, Canada

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I am surprised that you can't find "phosphated and oiled" hardware. You could probably strip the cad or zinc easily enough with muriatic acid. If the bolts are not hardened you wouldn't risk hydrogen embrittlement. If they are, you can very greatly reduce the possibility by immediate baking. But the bare bolts will rust almost instantly if they are not phosphated and oiled. Better to go to a plating shop with your zinc plated bolts and have them do it.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
 

I used to be in the fastener business and one of my competitors was "caterpillar" (same company that makes the big tractors and earth movers) they sold Black phosphorous finished bolts of just about any size you want and as I recall they claim that their bolts, washers and nuts don't lose their true temper since they don't go through any additional plating process, such as cadmium and zinc. I am not sure if you can buy them individually or in bulk from the Caterpillar company you might have better luck buying them from a commercial tractor, heavy equipment, or earth mover repair facility. good luck.

Pierre Rodgers
aerospace - Lompoc, California, USA