Join Date: Apr 2006
Thanked 147 Times in 144 Posts
Rep Power: 11
John, it could be that the alloy rusts, some "stainless" does. Or it could be contaminated with iron, the result of someone polishing it with wire wheels or "steel wool" which embeds tiny splinters that rust. When stainless parts are machined or formed on carbon steel tools, they also get splinters in them that can rust.
The solution is to "passivate" the stainless, which is done by picking it in acid (traditionally strong acid...IIRC muriatic, sometimes citric acid now in an effort to mollify the EPA) to etch out the contaminants.
That requires taking the winches, or at least the parts that are rusting, off the boat and to a "plating" shop that does chrome plating and/or anodizing, and asking them to process the parts for you. Passivating may or may not solve the problem, if the alloy itself is part of the problem you would also need to have those parts rechromed, or replated with something else to seal them. If you check your yellow pages for some plating shops, ask about dropping in and showing them the problem, they may be able to recognize it on sight.
The bas news is...money. The good news is...you'll have real pretty winches with a new durable finish on them and no more rust.