Yellow / Brown liquid bubbles / rust through sealer?


New Member
I have two spots on my 70 chevy cab corners that keep popping through sealer in the same place. I replaced cab corners and that is along the seam. I did notice that the welder did not like that area. This small rust popping through started once before so I sand blasted it on the inside and out and re-sealed (ds & ps). Here we go again. Obviously I'm going to have to cut this out but I've never seen rust like this. As highly as this sealer is regarded I'm surprised that in less than a month its popping through again, in my garage. The tech sheet calls for one wet coat as a sealer, I wondered if I didnt get enough the first time. It got two coats (30 mins apart) for full coverage the last round just to make dang sure I had enough on it. I let the stuff induce as Barry has mentioned for ~ 2 hrs, used spi wb wax & grease and let sit for ~45 mins. Was in 70-80s both times. I use the accuspray gun with filter on the gun and water separator out of the tank. IDK

I think its metal problem and I just need to cut it out. Certainly no pro with painting or even close to that so I try to follow the directions exactly.

Somewhat of a bubble forms and it has a yellow liquid in it. What is going on here? I posted two of one side (one zoomed in) and a third pic of the other side of the truck right on the cab corner body line.

Discouraging but I know I'm not going to move past this stage without it all being right. Glad to see it now before going to town on body work & all but still stinks.

I would also like to know if I cut this out, can I spot seal this area without having to spray the whole panel? What is the process to do that? Scuff up a few inches out from the panel and just give it a good coat (following all the steps in the tech sheet of course)? Should I tape off the area around it? Obviously its all going to get scuffed prior to filler work so im not sure if I need to worry about getting sealer over sprayed on to nearby unprepped areas.



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Promoted Users
Your welds have a lot of porosity shown in your pics imho. Generally caused by poor metal prep prior to welding. Metal needs to be clean and shiny on both sides. Are you using a flux core welder?

All that water base wax and grease remover wicked into that porosity and was trapped when you painted. It worked its way out causing the failure you see imho.

Porous welds are destined to perform poorly imho.

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New Member
No I'm using mig and it really didn't seem to be poros except in those two spots. Like I mentiooned previously, when I was welding up those corners it was splattering a lot so I think its some bad metal in there. I dont have a lot of porosity anywhere else so I think it was something to do with that area.