Advice from self taught welders?

NorseDave said:

Crackers said:

Speaking of which, make sure your panels aren't galvanized. Lots of (or most) newer cars are galvanized. In addition to being deadly, the galvanizing will boil and off gas blowing all of your molten metal out of the puddle. With sheet metal it will act like burning holes even if your welder is set up properly. 

So how to handle newer galvanized body panels?  Wire wheel it off (whilst wearing a respirator obv)? 

It's really hard to get galvanizing off sheet. I actually don't bother, just wear a respirator and deal with it, but that's with tons of practice doing things wrong. It can be welded, it's just hard to learn puddle management when you're fighting all the zinc burning off. 

 If you're trying to remove it for practice, you can use muriatic acid to dissolve the galvanizing. But it does have to soak, and the acid fumes will rust everything in the room, so do it outside.

I've heard you can remove it with vinegar, but no practical experience there.

NOHOME said:

gearheadmb said:

. The problem with flux welding sheetmetal is that flux wire makes slag. It's incredibly difficult to run a continuous bead on thin sheet, that's why everyone does the stitch (a line of tack) welds. When you are doing this each tack has to stick to three pieces, your two pieces of metal, plus the last tack in the line. With flux wire your last tack has slag on it, and your next weld wont stick to slag, just lay on top of it. So for it to work, you need to clean the slag off of every tack. That isn't a big deal if your going to do a small rust repair once in a while, but it will suck big time if you are installing two full floorplans in a car that need around twelve linear feet of weld each. 

 

F

 

That was the line of reasoning that I had compiled in my head for why flux core was not ideal for tin. Then Crackers proved me wrong so I guess something in the above argument is not correct.

 

I suppose if doing a long weld seam you could do a tack, skip to the next and then clean off the slag from the sum of tacks and repeat, at least you would be doing more than one tack per cleaning session.

The other approach I considered was to reverse the workflow a bit. Rather than laying the next tack on the side of the last one, start a bit off to the side at a slag-free location, and do a slight move towards the last tack. The approaching heat might boil off the slag and allow the newly deposited metal to wet into the previous tack. Just a thought.

 

I think I may have mentioned this before, but I was taught how to weld sheet metal in an auto body class at a vocational school, with a FCAW, so never thought there was anything unusual about it. LOL Once you get it figured out it's not that much more work.

NOHOME said:

I suppose if doing a long weld seam you could do a tack, skip to the next and then clean off the slag from the sum of tacks and repeat, at least you would be doing more than one tack per cleaning session.

That's the way I did it. So if you tack every inch, you have a nice line of tacks that are easily cleaned. And it gives the tacks a little bit more time to cool off before starting the next set of tacks.

For small galvanized parts you can use any of the phosphoric acid rust converters to remove the zinc.

I'm not sure if brushing a bit on an area to weld would do much, it usually takes 15 minutes of soaking to remove it from plated fasteners before I weld them.