PSA: welding a cracked header tank with a mig gun instead of tig cost me 2 days of rework

I had a 40-gallon header tank with a hairline crack near the seam on a job in Gary last month. Thought I'd save time by zapping it with my mig instead of dragging out the tig setup. Looked fine after grind down, but when we pressure tested it the next morning, the weld blew out and sprayed water everywhere. Had to cut the whole patch out, clean it proper, and run the tig bead slow. Lost a whole day and a half. Anyone else learn this lesson the hard way or got a trick for when mig works okay on thin tank steel?

3 comments

3 Comments

angela_harris1mo ago

48 hours and a mig patch ain't worth it on thin header tanks.

sean_cooper581mo ago

Had a 60-gallon tank in Newark do the same thing to me... mig just doesn't get hot enough on the thin stuff near the seam. I switched to tig with a silicon bronze rod and it held perfect on the first try.

keith9001mo ago

Lincoln welders near me had the same problem you're talking about on a 40 gallon tank. I was dead set on MIG being the answer for everything, but that thin seam near the bottom just kept blowing through no matter how much I backed off the heat. Silicon bronze on TIG never crossed my mind until a buddy at the shop mentioned it. Tried it on a scrap piece first and couldn't believe how clean it laid down without eating through the metal. You definitely changed my mind on that one, MIG has its limits. I'm stocking up on silicon bronze rods now for any thin tank work.