Black and white welds

Hi guys, could any of you tell me what's going on here.

I bought some 0.9mm sheet that was described as CR4. I'm using Argon CO2 mix (which is definately flowing) and 0.6mm solid wire.

The material seems to produce a lot of black type soot (messed up the torch in quick time) and a white powder that forms a spiders web type of coating. It all cleans off, post weld, but isn't right.

I did flap disc the material, but still got this mess (perhaps more taken off?) Anyway tried on some other scraps of steel and no white mess.

What's causing it?

Im not sure but that could be galvanised or coated in some other way.

I suspect it is a galvanizing issue, but not managed to find other examples, so looking for confirmation. Thing is the sanding didn't seem to help much.

The white stuff underneath looks like the stuff you get welding a zintec coating. There's not normally that much of it - maybe an extra-thick coating or it's galvanised.

Zintec is normally a very thin coating in a greyish colour a bit like this photo, and it is fine to weld so long as you have a little ventilation. Yours looks more silver like galvanising. You can normally see a crystal pattern if it's actually galvanised - for that you'd need to get both sides of the weld back to bare metal.

I'd say thats galvanised. Cobwebs blowing around when you weld? Got the sniffles?

Doesn't look like that zintec, looks like a normal steel colour.

I've had another go at removing the coating and under artificial light it just looks like you're polishing the metal. Under natural light there is what looks like a feathering of a coating, but it's barely noticable.

Welderpaul, I was outside, and any breeze that was there was on my back, so don't think I've breathed in anything nasty. No headaches or flu like symptoms.

I would say galv also, I had similar on a fan housing I welded together even though I had put a flap disk to it.

Originally Posted by eil I would say galv also, I had similar on a fan housing I welded together even though I had put a flap disk to it.

I don't feel so daft now.

Zintec i would say. CR4 should have no coating except for some ligtht oil.
Where did you buy it from?
Surelly no one that sells steel is foolish enough to get confused? They look completely different, galv,zintec,self colour... 3 different colours.
CR4 is a 'steel' colour with a bit of a sheen, galv is quite shiney, with a coating that looks like flakes, zintec is almost matt, a whitish blue/grey colour.

Although if youve flap disced it, it might be just a thin layer of galv, so same symptoms of zintec.

Yep definately galvanised! there's a word for those white flufs.... but i can't recall it at the mo...