Welding Tips and Tricks

I'm a novice TIG welder and I'm trying to figure out what is going on. I helped someone by TIG welding something on their winch bumper and even after sanding with a flap disc and wiping everything down with acetone there were still contaminates in the metal that would burn out when I started welding. Did I not prep something right or is it just oils and other crap impregnated in the pours of the metal? What can I do to prevent this in the future?

Thanks

Pictures please.
Could be the machine or the metal.

I am in for pictures as well. There are allot of things that could be happening.

machine, setting, filler??
craig

was it galvanized ? I recently had a prob like that. Flap disc'd off all the galvy ...still was messy

One thing I encounter a lot is a surface prepped by media-blast, and primed with a zinc-bearing primer. I find these exceedingly difficult to prep for welding. (Even a non-zinc primer on a media-blasted surface will make soot when you weld it, but zinc is a bear!) I have to define precisely where my weld is going to go, and grind it deeper than normal prep would suggest. To no weaken the area outside the weld zone, I have to leave the contaminates in place, and deal with the crap boiling off the sides. This makes it difficult to see clearly what I'm doing, and particularly suck in a lap-weld as crap will still boil out of the HAZ under the lap.

I'm not saying this is what you encountered, but it is one possibility.

Steve S

Unfortunately I can't get any pictures. I was thinking though, It seemed like at first it welded fine but after a while it would start boiling. I didn't clean the back side of the welded area before I welded so could it be that once the area heated up it started to penetrate all the way and that's where the contaminates came from? On some of the areas I ran several beads and the first one was beautiful and the second and/or third didn't. I don't remember the settings exactly, but it was around 125 amps and 1/8 mild steel. I used 3/32 ER70S-2 filler rod.

Yes that is a likely event.