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I Forge Iron

Heat Bluing Stainless Steel


dagr8tim

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Yes, this is an odd one.  But I'm sure somebody here knows the answer.

I've got a stainless steel knock off Yeti tumbler (Walmart Brand).  Awhile back, I used an electrochemical method to destress an area after I had applied a decal as a mask.  Today I got wondering if I could hit it with a propane torch and blue the rest of the tumbler to give it a worn sorta rusty/corroded look.  Things went well, until I brought it in and washed it in the sink before drinking out of it.  Alot of the straw to blue that color change I was going for washed off with a simple dish sponge with little plastic nubs.

Is it possible to get the effect I'm after while keeping the tumbler food safe?  I'm only doing the outside, and not the inside of the tumbler.  Or is it just the way of things that the discoloring will scrub off over time?  I know that it's a thin layer of oxide.

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My understanding (from watching videos of them being cut in half) is that it is basically 2 stainless steel cups that nest and are attached at the top lip and have a vacuum drawn in the space between.

Edited by Mod30
excessive quoting
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Be aware that if you heat it up into the sensitization range (assuming don't have a stabilized or L stainless, per the source and application), you will precipitate chromium carbide into the grain boundaries. This will make it stainmore steel, and it may corrode aggressively at the grain boundaries due to the absence of sufficient chromium to form a dense and adherent chromia layer.

I don't recall the relevant temperature range off the top of my head, but I have given enough information for you to look it up if you care. I am boarding a plane, or I would look it up myself. 

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Yeah, even a Bernzomatic butane torch can bring thin sheet to yellow. Another thing to think about is what happens when you lower the structural integrity of a structure holding a vacuum.

How many of these cups do you have to experiment with?

I'd see about electro chemical patination. I know it works to produce from mirror polish to very dark brown to black but not other colors.

Keep us in the loop please, we're interested in what you learn.

Frosty The Lucky.

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