brown-reddish treatment

[petersi]

Hi,

I have been searching around but still can't figure what kind of treatment on this steel/alloy steel/stainless steel. I would like to know what kind of treatment making the color brown-reddish. It is not powder coating. Any idea? thanks

 

[TomDOT]

The photo is small, but that looks kind of like copper plating.

 

[tnatale]

It looks more like a conversion coating. Are you sure it is a steel substrate? I've seen those types of colors on Al.