hardware help 2- related question

[fairchild]

This is sort of related to the previous post-
Occasionally doing non-aircraft related things I find myself wanting to use a bolt, nut or washer integrated into something via Tig welding. The main problem is the coatings that
every bolt or nut has on them. The Tig electrode is very picky about contaminants on the work- I have tried soaking nuts or washers in a small container of lime away- thinking the acid
in it will dissolve the coating down to bare steel. I think that is getting either some or most off but not sure about 100%. Tried grinding but that smears a residue around- enough to
get a bad reaction when you go to weld. Are there solutions made to strip off plating in that manner ? I don't gas weld much anymore now that I have a tig machine- but I think
most of those plating materials would cause problems gas welding too- not to mention creating poisonous fumes ....... (that's no fun either)
Any tricks for removing plating ?
Tim

[dedgemon]

scotchbrite wheel. not a perfect solution, but mostly works

[alaskabearhawk]

I just make my washers out of 4130 sheet stock.

[dedgemon]

I'm pretty sure you can buy unplated hardware if you really want to. I've gotten some from Spruce and I suspect that there are other good web sources. Usually I'm in more of a hurry and just knock it off with the scotchbrite and go my merry way. Of course using AN stuff for pedestrian projects is a little pricey but I've generally got a good bit of it already, so that's what I tend to use.

[jaredyates]

Try phosphoric acid. It works great for removing zinc plating but not damaging the underlying steel. Around here you can get it in the paint section of Home Depot, and it's also the active ingredient in many rust removers, including naval jelly.

[fairchild]

I think phosphoric acid would remove the coating but it would leave a conversion coating of iron phosphate on the surface of the steel. Last nite I tried soaking an aluminized exhaust tube in some alumiprep-like stuff for cleaning aluminum boat hulls (called toonbrite) - that took off the aluminum wellfor making a welded exhaust joint.
tim

[jaredyates]

I think phosphoric acid would remove the coating but it would leave a conversion coating of iron phosphate on the surface of the steel. Last nite I tried soaking an aluminized exhaust tube in some alumiprep-like stuff for cleaning aluminum boat hulls (called toonbrite) - that took off the aluminum wellfor making a welded exhaust joint.
tim

I'm not a chemist, and didn't even stay in a Holiday Inn Express last night, so I can't speak definitively. The phosphoric acid leaves behind a slimy black residue that mostly wipes off with a rag, or if it's really stubborn, a stiff-bristled scrub brush. I don't know if the black stuff is the iron phosphate or not. The most important thing is that you don't do much welding around the zinc plating, due to the health hazards of zinc poisoning.