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Warning: An old timer in Gary told me my weld prep was too clean
He said on the old 2-inch thick plate we were working, a perfectly shiny bevel could cause undercut on the first pass. He told me to leave a light mill scale, maybe a 32-grit scratch finish, to give the arc something to bite. I tried it on a pressure vessel job last month and my root passes stuck way better. Anyone else get that kind of counterintuitive tip from the older guys?
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cora1772mo ago
Ever tried that on rusty pipe?
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the_tara2mo ago
Guess the arc likes a little grit.
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hill.david1mo ago
Wait, rusty pipe? Like, the actual metal kind? That's a whole new level of grit, @cora177. I've seen people use it on old brick or maybe a concrete step, but pipe rust is a different beast. That stuff flakes off and leaves such a rough surface. You'd need to prep it for days just to get a smooth coat. Honestly, the idea of paint sticking to that long-term makes me nervous.
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