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Old 05-31-2012, 11:43 PM
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Tiny pinholes in sheetmetal welds

Hi, I've been a lurker on here from time to time, but now I have a question. I'm working on a '68 Charger doing rust repairs. The following pictures are of the trunk gutter. The tail panel has been removed.

The problem that concerns me most at the moment are these small pinholes I get in my welds from time to time and why they are happening, how they can be prevented, and how to address the current ones for epoxy and paint. Most are not completely through the material. The pin in the last pic is a small T-pin I use mostly for probing electrical connectors and is there for size reference.

I will include pictures of the whole process of the patch replacement as I do not know where my mistake is at. I'm using a Hobart 140 MIG with 75/25 gas set at 20 CFH with the trigger pulled, .023" wire, and I ground down the tip of the gun nozzle even with the contact tip, so I could see a bit better. I use tacks the whole process and planish them ASAP then cool them with my air gun for a few seconds.

The replacement patch was made from 20ga sheet steel. Machine settings were 2/30-35. I do not move the gun at all when tacking, just hold it perpendicular to the surface, aimed at the gap. I don't always trim the wire after a weld, but sometimes I will.

Any questions, just ask. Any help is appreciated. Thanks.

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