Welded Rust --- what is it?

[MNAirHead]

Welded Rust....

This weeekend was welding some rust on a body-off car. I found a little rust underneath.... welded it... it pooled OK ... then did the surrounding metal... cracked it with a hammer and it seemed solid.

Is this OK to grind and paint...common sense says no...the other side says if it's solid and sealed then it should be OK.

T.

[Kubel Nick]

Need more info, it could be just surface rust.

Best to remove any rust to minimize contamination of the weld bead. If it starts to rust enough and make the metal thinner it usually just burns through like butter when you try to weld it.