Steel Color

[rick67]

OK I'm curious of why this hatchet has this grey almost blue color. It spent a week being cleaned with electrolysis. It showed right through rust when I dug it up. I thought it was a paint layer that would disappear as the rust dissolved. At first it seemed to as in the first picture but as it sits the coloring is coming back.
Its not the first time either. I found a old pick axe once, same color, completely void of rust. Don't have pics of that as I left it with no desire to lug it out.
Any help appreciated.

 

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[Tony in SC]

When I clean heavy rusted engine parts they turn black because electrolysis produces hydrogen sulfide which turns iron black.

 

[rick67]

I hear ya, hand forged items I get turn black. The irons like above, more brown.
Just don't get the grey/blue. The almost 1/4" of rust was off colored also. I'm guessing its something done different at the foundry.

 

[Tony in SC]

Must be an alloy. Some iron has as tin added to make it strong and hard. Some has nickel to make more machinable.