I was watching one of those shows, either “How it’s made” or something like that. Anyhow, I think they were talking about making something for the aerospace industry and they showed several processes to the metal part, one of the processes turned the silver-looking metal(I think it was aluminum but I could be very wrong, it’s been a long time since I saw it) into a gold color, which they said was a result of one of the treatment processes. The part didn’t look like real gold, but it did have a gold color. I think they said it was something done to increase durability or reduce wear.
Probably chem film which gives a goldish color but looks very different than the gold bearing.