Weird TIG Weld

I have a small ongoing production job that requires me to TIG a piece of stainless bar stock to a piece of lightly galvanized steel and I have never had an issue doing this prior to today. I was happily welding along when the puddle "fizzed" and the arc changed color. I stopped to flip up the helmet and noticed a glob of material had jumped onto the electrode. There was also a corresponding low spot in the weld. I concluded the electrode had simply touched the puddle so I broke off the lump, reground the tip and went back to work. A couple beads later, the same thing happened. I said a bad word and repeated the electrode dressing. Three or four welds later, it happened a third time. By this point, the electrode was pretty short and I was insane with rage so I went to the box to get a new one. After changing the electrode (which came from the same box as the other one), the problem went away and did not happen again over the course of about 20 more welds.

I'm stumped - I may have touched the puddle in the first instance but I'm pretty sure it did not happen the second and third times. The only thing I can think of is that the whole electrode was somehow contaminated but I have never seen weld metal jump to the electrode unless the puddle is touched. Has anyone had a similar experience or am I just whacked out today?

I've actualy seen the drop of filler get attracted to the tungsten a few times. Mostly when doing aluminium on AC. I'm not sure how it happens. Maybe it creates a strong enough magnetic field to drag a little drop of metal up.

I was welding dowel pins to vise grips to make a "pinchoff" pliers...for pinching a hose without damaging it.

The galva-whatever plating that's on the vise-grips jumped up and stuck to my Tig electrode...

Then...it redeposited on another job...yes I deserve a dope slap for not regrinding my Tig electrode back to good but see the little orange spots in this bracket weld. I think it definitely interfered with the top weld...it looks like a piece of bubble yum blasted on there at 60mph.

Matt, I would just call that "on the fly" rust proofing!

I think its the zinc in the galvanizing, too.
That stuff often will snap crackle and pop, and levitate, when you try to tig it.
If it isnt a real high strength part, I use a silicon bronze filler rod, and tig braze galvanized parts. It works well, and cruds up a whole lot less.
Otherwise, try physically removing the galvanizing- wire brush, grind, or sand it off.

You should remove all galvanization before welding. The melting temp of zinc is about 790F. Once molten its vapor pressure is above atmostpheric, and will immediatly boil, leaving porosity and can cause short term health problems.

NK

"By this point, the electrode was pretty short and I was insane with rage "

Dang, man, I get a little put out at times in the shop but I'd never say I get insane with rage! I always figured if I ever went insane with rage they'd be scraping body parts out of the grille of my dually or something.

Again, it's the zinc.

Zinc + weld = nothin' but trouble.

(sloeit, since you seem to know... What is that weird weightless white zinc soot shyte that is formed and floats through the air? Is that zinc oxide, or just zinc soot?)

And while I'm at it, why the heck does zinc do that? It isn't just you, Wooldridge--- Zinc actually jumps off the job onto your electrode. You didn't dip it. I've never understood why.

I had a similar thing happen today. I was welding a 94" extension to a stainless table top. The table top was two pieces and the extension was one long piece. I started at the right hand side and welded the length of the first half of the table top with no problems. I got about 6" into the second half and there was a flash followed by a hole in the table top. Upon examination of the tungsten I saw it was contaminated with what appeared to be stainless. This frustration continued for the rest of the weld on the table. There seemed to be some kind of impurity in the base metal.The weld would go along good for a few inches then a hole would blow out.It left me frustrated and wondering what the hell the problem was.

The job I'm doing is on small parts so I started sandblasting the pieces in the cabinet before welding. The problem has now completely gone away so it appears the thin galvanizing was the culprit. Another thing I noticed is that there previously were hard spots in the weld area and those have also disappeared. I suppose the galv was making some sort of hard oxide in the weld area.

Dr. Rob,

That white soot is from as far as i can tell, zinc oxide. Not too good for you. Your body can remove zinc from your body, so its not a heavy metal cumulative toxin, but it will give you "metal fever" i believe its called. Ive HEARD its like having the flu, ive HEARD drinking milk helps. YMMV

It would seem to me that the reason it seems to jump to the electrode is because the zinc, once melted boils. Melting temperature is about 790F, molten steel, ~2500F, center of an electric arc 30,000F. From what I can best figure, it melts, is superheated and boils violently, throwing contaminates onto the electrode, and stuff in reach.

The zinc is boiling because the vapor pressure is above atmospheric at normal (melting) conditions. Waters vapor pressure is equal to the atmosphere at 212F, basically why it boils.

Hope this offers some insight, and makes sense.

NK