by bartonmd » Tue Aug 05, 2014 6:33 am
I didn't see it before, but the little bit of porosity is from one of two things:
1. Paint still on the surface where you were welding.
2. Slag/dross from a torch or plasma cut edge. I use a plasma a lot, and it's MUCH better than a torch, but before you weld on a plasma cut edge, you need to grind the hardened, aerated steel off of the very edge. You don't need to grind 1/2" off of it or anything, but just run a grinder up and down the edge once or twice and it'll get enough of it off that it won't cause problems. Since the head-affected edge is bigger on a torch cut, you need to take a little more off of a torch cut edge, but it's not bad either. Just go until you see freshly ground metal with no bubbles in it.
Mike