Posted by Matt Wilson [108.162.221.33] on Sunday, July 24, 2022 at 23:16:30 :
In Reply to: Re: Chrome plated fan posted by Todd Miller [172.70.211.70] on Sunday, July 24, 2022 at 14:20:52 :
Chrome plating (actually many types of plating), applied to high-strength steels and some other metals, introduces hydrogen into the microstructure of the steel. The hydrogen molecules tend to congregate in areas of high stress, producing internal pressure in those areas. At that point, it often doesn't take much stress to cause failure of the part. I've even heard of parts cracking on the shelf, before even being installed. As I mentioned before, when it comes to steels, this is mostly an issue with higher strength steels - i.e., those with ultimate tensile strength greater than around 140,000 psi (hardness greater than about 30 Rockwell "C"), just a little lower in strength than a Grade 8 bolt. Hydrogen embrittlement can also be caused by other processes such as welding, and it can come as a result of conditions in service, such as corrosion from moisture exposure.
In manufacture, the potential for hydrogen embrittlement is usually minimized by baking the part at a few hundred degrees within a certain period of time following any potential hydrogen-introducing operations.
In any case, most parts on our old trucks are not made of steel that is of high enough strength for this to be a significant concern. I still don't think I would plate a cooling fan, but I also doubt it would be a big risk if I did. It's just one I'm not willing to take.