I'm going to make a teapot out of stainless steel. It may or may not be used as a teapot (IOW, the intent is to make it decorative), but I'd like to know what's needed to make it safe to drink out of.
If I don't back purge and the inside gets oxidized, will it be safe to use for drinkable liquids? Any specific type of SS I should be looking at - anything required for "food grade" use? Anything I'm missing?
I'd say that you'd want a crevice free interior for sanitary reasons. The brazing filler metal should flow pretty well and the flux residue will be soluble in water so it will be easy to remove. GTA welding with an interior purge should be OK too, but you might need to dress the welds by grinding to make sure you have no crevices. Not such a big deal if all you ever use it for is water. But who knows what'll happen way down the road. I think your bigger problem will be keeping the joint closed tight while you're joining it. Thin gages tend to spread as you weld along. You'll need lots of tacking if you're welding. The brazing might be better done in a furnace with a preplaced filler metal insert and weights to hold the joint shut.
You should be fine with a standard austenitic stainless steel, 304, 304L,
316 or 316L. The 304 is a standard food grade. The others help with corrosion resistance.
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