Saw a guy in my shop put Bondo directly over bare metal without any etch primer

Is it just me or does that always crack out within 6 months and then you're doing a full strip and redo?

3 comments

3 Comments

Read an article from a corrosion engineer once that said bare metal plus Bondo is basically a moisture trap waiting to happen. The way he explained it, the bondo itself is porous enough that water gets in through tiny scratches and then sits right against the steel with no protection. Etch primer or at least some epoxy primer gives you that chemical bond and seals the surface so moisture cant get underneath. Ive seen guys skip it because they think the bondo sticks fine without it and sure it might hold for a year or two but then you get that nasty blistering from the backside. Makes me cringe every time I see someone slapping it on raw metal like that because its just gonna mean more work later.

angela7284d ago

Oh, that just makes my stomach sink when I see that. You know you're looking at a repair that's going to fail, it's only a matter of time. @hunt.hayden is right about the moisture thing, I've seen it happen more times than I can count. I had a neighbor do it on his truck fender, looked perfect for about eight months, then one winter the whole patch just bubbled up and started peeling from the edges. He ended up having to grind all that bondo out and start over from scratch, which cost him twice as much in the end. It's such a common shortcut, but it always comes back to bite you.

torres.riley4d ago

Yeah I totally agree, I did the exact same thing on my old Civic back in the day. Spent a whole weekend sanding and filling a rust spot on the quarter panel and thought I was being smart by saving a step, sure enough about nine months later it started bubbling up from the inside out. Ended up having to cut the whole section out and weld in new metal, which was way more work than just doing it right the first time.