Bondo over primer?

[Canonman67]

I hope I don't sound too stupid but when I was a kid we'd strip off the paint and put bondo on bare metal. Now I see that people are putting down a primer and then bondo over that. Is that the proper way? I trying to avoid the issues I had from the previous owner where the filler was cracking and falling off. As always thanks for the help.

Lionel

[tac]

The thinking is epoxy primer prevents moisture from getting to the metal and will bond better to metal than the polyester fillers.
So primer then filler.
Polyester filler then primer was when the primer was lacquer and didn't bond or seal as well as the polyester filler.

I have to go look, but I think if you read the filler instructions and epoxy primer instructions they contradict each other.

[Dave Severson]

I still do it either way, just depends on the situation. I did have a PPG rep tell us all at a seminar last summer that their preferred method is filler over epoxy primer, then he qualified it to say that it really didn't seem to matter...... The epoxy primer does an excellent job (as mentioned) of sealing out moisture from getting at the back side of the filler.

[Canonman67]

Thanks guys. I wasn't sure what was right, since it doesn't seem to matter it's all down to how well I prep everything.

[tac]

Thanks guys. I wasn't sure what was right, since it doesn't seem to matter it's all down to how well I prep everything.

Yep,
Preparation is the golden ticket.