Stovebolt.com Forums The Shop Area Paint and Body Shop Applying bondo prep

I know this has probably been covered but there are so many threads I have not found what I need. I just replace the cowls on my 54 1/2 ton. The top seam that was leaded at the factory now needs to be repaired. I will be using bondo ( or comparable product, if there is one). I will be getting it from my local auto paint store.

After cleaning the area of rust and old paint should I prime it before applying the bondo?
Should I chemically clean it with anything? Acetone?
Should I drill random small holes so the bondo has a solid grip?

Here is an earlier post on this subject.

Check the instructions for the filler you plan to use.

I think that traditional bondo on bare metal might allow rust.

I think it is prudent to use most "traditional" fillers on top of epoxy primer that has been applied to shiney cleaned metal.

Your local auto paint store will have tech sheets for each product. But that won't help you with technique.

Most body working books are also very outdated. Youtube can be a good place to go to see what processes people are doing these days, and to witness some techniques.

Tim is correct- bare metal, then epoxy, then filler, then primer(s), then sealer, then paint - seems to be the favored process these days.

If you have to drill holes through the metal to hold the filler, then you need to get out your hammer and do some more panel straightening. Don't use thinner or acetone to prep bare metal- there are products specifically designed for this. Bare metal is typically sanded with a DA sander with correct grit paper to prep and provide a tooth for primer/filler to bond properly. Or sand blasting.

That said, if you're not looking to invest a lot of time learning the process, and/or investing in the tools and materials (which are kinda pricey), there must be a few quick and dirty methods to deal with it that won't cause too many people to shudder in horror....or have it fall apart in a few months...but I just don't know what those methods are. Perhaps someone here will have some easier ideas.

I believe that for most body fillers, 1/4" thick is the absolute limit. IMO, that is crazy thick.

Whatever you do, be sure to get as much info as you can from the paint store reps- some products are not compatible, such as epoxy products and anything with acid in it, such as etch-primers. And by "not compatible", I mean that it will de-bond and turn into to freaking mess (sometimes in very short order).

Sorry, Dave,

Your sequence is : "bare metal, then epoxy, then filler, then primer(s), then sealer, then paint"

With the PPG product-lines we used, we followed this sequence:
" . . . fillers on top of epoxy primer that has been applied to shiney cleaned metal . . ."

derusted, repaired-as-needed shiney "washed" "bright" metal
then epoxy primer
then sealer/surfacer
then urethane top coat (two-part urethane, single-stage application)

Tim, no hi-build primer? The epoxy I am using requires metal to be prepped with either 80 grit on a DA, or media blasting, in addition to being cleaned. I haven't worked with PPG before. I guess every product manufacturer has its different requirements.

As far as filler, I cant say enough good about Rage Extreme (Evercoat), so much better than bondo brand

Agree with sstock. I used Rage Ultra and really liked it. I think the Xtreme is probably better than the Ultra. Couple of bucks more anyway. I got stuff like that from autobodytoolmart.com. You might want to check them out.

Dennis

Bare metal needs epoxy primer. Body filler goes on epoxy primer (after it's been scuffed to give it mechanical tooth). Urethane high build primer goes over body filler and scuffed epoxy primer.
Do not open a can of chemical before reading the manufacture's technical data sheet and fully understanding what they instruct about sandpaper grits to be used, dry times etc.

Do not ever drill drill holes in the body to give the body filler an anchor. This is the best way to get your body filler to pop off the metal after you've painted it. This will happen every time because the exposed filler will absorb moisture and swell the filler while it rusts the steel from underneath.

Thanks everyone. I would have done it wrong. Any opinions on All-metal? This is the product my local paint/body store carries. It is advertised as a replacement for classic cars and lead seams.

You could use it... may ask them for some cans of spinich to go with the all metal.

That'll help pump the arms up ala Popeye.
Personally I'd be looking for another shop if all mine offered was that.