An old timer in Mobile told me my weld prep was too clean

Back when I was a helper, maybe 15 years ago, I was grinding a bevel on a 6-inch pipe for a boiler feed line. I had it polished like a mirror. This old fitter, Frank, walked by and said, 'Kid, you're leaving it too slick, the bead won't have anything to bite into.' I was confused because I thought clean was best. He showed me how to just rough it up with the grinder, leaving tiny grooves. I tried it his way on the next joint, and the penetration was way better. Anyone else get a piece of advice that went against what you thought you knew?

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4 Comments

ericw936mo ago

My uncle swore by a little surface rust for paint adhesion.

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jade_shah796mo ago

Guess that's why my old fence looks like modern art now...

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michaelcooper6mo ago

Your uncle's advice sounds like a shortcut that could backfire. Does he mean just a light orange dusting, or are we talking about real scale? I've seen paint bubble and peel right off a rusty lawn chair because the rust kept spreading underneath. How does he prep it? Just a wire brush, or does he use some kind of converter first?

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torres.blair4mo ago

Oh man, that totally reminds me of when I first started painting cars! I was sanding a hood down to super smooth bare metal, and my boss told me to stop. He said the primer needs a little "tooth" to stick, just like your weld! I went over it again with a rougher grit and you could just feel the difference. It's funny how the perfect surface isn't always the smoothest one.

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