[TheForge] Putting an oxide finish on mild steel?

[Aaron Stavens]

I'm pretty new to metal working so I'm not even sure where to look for
info on my questions. I'm hoping someone here can point me in the right
direction. I'm trying to put an oxide finish on some mild steel and I'm
looking for a good way to do that.

BACKGROUND:

A friend is making a clay sculpture and has asked me to fabricate a wall
mounting bracket for the sculpture. The sculpture will hang indoors. I
made the bracket out 3/32" sheet steel. I think it is mild steel, but
I'm not sure since I pulled it out of the scrap pile. The surface is
covered with RG45 weld beads. The weld beads are my doing.

I had another different piece of sheet steel I had welded on with E6013.
I had baked it in my kitchen oven and, unintentionally, it acquired a
dark blue color with purple and copper highlights. There is also a nice
iridescence in places. My friend saw this and liked it. So, I'm trying
to achieve a similar effect on the bracket.

I figured I would buff the bracket with a wire wheel and bake it in the
oven like I did with the previous piece. The baking didn't go so well.
All I could achieve was a very light translucent blue even after hours
in the oven. I assume my oven simply isn't hot enough, but I'm already
running it at the maximum of 550F. I also tried heating the bracket with
my welding torch. I achieved a whole rainbow of colors, but I couldn't
seem to control the colors I achieved.

QUESTIONS:

1. Is this type of oxide finish on mild steel stable in the first place?
If not is there a way to stabilize it?

2. I was planning to put a coat of lacquer on the bracket after I
achieved the desired color. The thought is the lacquer would prevent
oxygen from attacking the metal further. Does this sound reasonable?

3. Do you think shining up the steel with a wire wheel is sufficient
surface prep or is there something else I should be doing?

4. Is there a chemical/patina treatment out there I can use to achieve
the desired effect instead of using heat?

5. Is there anything else you would like to suggest?

Thanks,
Aaron Stavens
Seattle, WA