When blocking out primer, if you end up sanding through to steel (through your etch or epoxy, whatever you used first), how big of an area of exposed steel would it take for you to go to the extent of spotting on some more etch or epoxy? Or would you use a metal conditioner on those areas instead? Or if it's not a very big area would you just re-prime with your primer-filler and not worry about it? Basically what would you say is your rule of thumb on sand throughs?

I ASSUME your not talking about an EDGE.
SO if you sanded through metal, you have a High spot you need to Fill the low spot area aroung it.
So re etch prime the bare spot and then re-prime the panel again.. 3 heavy coats of your high build primer should do and a guide coat of your favorite contrasting rattle can paint

Would you re-etch a sand through on an edge also?

on an edge.. YES I would re etch.. get your self a rattle can of etching primer ..if possible from your local Jobber...

Have you ever tried just treating those areas with an etching metal conditioner, and then just re-applying your primer/filler? Pros/cons?

A metal treatment is a bad idea!! No pro's to it just all cons's

Stick with your regular etch or get a spray bomb form of etch.

Why is it a bad idea? As far as the products I have been using (DuPont URO primer/filler), according to the tech sheets they recommend treating bare steel with their 5717S (I think that number is right) metal conditioner, that is if you were applying that primer to bare steel. Do you think the surrounding primed area would tend to absorb some of the metal conditioner and cause some problems down the line?

Ok, what product have you been using on bare metal?
A metal treatment or etch? What did you cover the metal with before the uro?

First I used DuPonts Variprime (their etch primer), then I applied the URO. The spot in question is no more than the surface area of a dime that I sanded through, and from reading over my tech sheets for each product it looks like I could either mix up more etch, or treat this spot with the metal conditioner before going back to the URO. I wasn't even sure if it was enough of an area to be concerned with. And thats when I came in here for advice.

Opinions please...

If you read the Uro tech sheet it says:
Treat bare metal with 2 coats of variprime OR metel treatments.
DO NOT combine the two products together it will just cause a adhesion problem.

Just get yourself a small can of etch in a spray bomb or load up the gun with variprime.
Forget about metal treatments its out dated!!!!!!

What the PPG reps have been pushing is an area about the size of a half dollar should be treated with etch.
But for you I wouldnt even worry about it, just apply more uro...Eric

A half dollar they say... well we are well under that. It is a small spot, but I didn't want to just assume that it would be ok, and on the other hand I didn't want to mix up additional product for such a small spot. I know not to use the metal conditioner under the Variprime, but I wasn't sure if treating an area with the etch already around it would cause a problem. The tech sheets can't cover all the screwey situations that one might run into, thats when I start asking questions in here from those who have the experience.

Thanks graemlins/waving.gif