...imagine, I was joking, of course.
Not sure if I'm mistaken, but I guess the traditional process of heat blueing steel is a chemical reaction - oxidation.
So, one could say they're "chemically treated"?
I know there are multiple ways to achieve the blueish tint.
BTW, in my oppinion the often heard "rust protecting" effect of blueing isn't really very effective (if existant at all) - I believe
it's more because rust is less visible on the darker surface - but's that's just my unqualified opinion only.
Best regards
Suitbert