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Appreciation post: The old guy at the parts counter in Fresno saved my hide on a quarter panel
Last week I was trying to fit a new quarter panel on a 2015 F-150 and the weld-through primer I had was making the MIG gun sputter like crazy. I called up the supply house and this older guy, Frank, told me to thin it with a capful of acetone and let it flash off for two minutes before tacking. It worked perfectly and saved me from grinding off a whole mess of bad welds. Anyone have a different trick for keeping primer from messing up your welds?
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clairem816mo ago
Frank's acetone trick works great, but sometimes I just skip primer and weld clean metal.
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jake_anderson246mo ago
Honestly, skipping primer is playing with fire. That acetone wipe gets surface oil, but it doesn't touch mill scale or oxidation. You weld clean metal, sure, but you're welding to a contaminated surface. I've seen welds look good then fail because the bond was weak from the start. Just grinding to bright metal takes a minute and saves so much headache later. It's the only way to be sure you got a real, clean base.
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valthomas5mo ago
How many times have you seen a weld crack right next to the bead? Jake is totally right. Acetone just moves the grease around, it doesn't get rid of the scale. That scale is like a barrier. Your weld sticks to the scale, not the steel. Then the scale pops off and your weld has nothing holding on. Grinding is the only fix. It's not extra work, it's the actual job.
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