Bare metal prep? Primer or bondo first?

Argeo · 01-13-2005, 08:10 AM

Just wondering what most people do to clean the care metal before they primer and bondo?

I always thought you bondoed first and then primered. Is that true?

Thanks in advance.

David

Tim Hancock · 01-13-2005, 08:23 AM

Some will claim it is best to put Bondo over epoxy primed metal, some will claim it is better to apply z-grip or etching type bondo directly onto the metal. I have done it both ways with satisfactory results. Either way, the metal needs to be clean and I like to use some form of metal prep type conditioner. On a steel car, I do not think it matters if good prep is done, but on aluminum (such as aircraft skins) I etch, alodine, then epoxy prime, then skuff, then bondo (not that you care about aluminum).

Argeo · 01-13-2005, 09:05 AM

Do you mean that a steal car does not need a veriprimer (not sure the spelling) before the primer that the paint goes on?

I am using that veriprime stuff which is ridiculously expensive and then painting over that with Nason Highfill 2K primer. Do I need to use veriprime?

Thanks.

widebody911 · widebody911's Garage

Bondo sticks best to roughned raw metal, and then primer over that. But you're putting on such a micro-thin layer that it doesn't really matter, right

Argeo · 01-13-2005, 09:16 AM

Ah, for the most part yes. I am trying to stay under a 1/8 of an inch but there is one area on the right rear quarter that when the end piece was replaced (from the tail light to about a foot in) the weld wasn't so good. The bondo might be a bit deaper there.

Unfortunately I do not have the time, expertise, money or patience to redo correctly. The paint that was on the car was probably 10 years old and I didn't even know this quarter panel screwup was there until I stripped it. If I can get it back to where it was, I will be happy. I am hoping that if the bondo slides in 10 years, maybe I can pay someone else to fix it then.

Thanks.

Willem Fick · 01-13-2005, 09:35 AM

From the school of hard lessons - bondo doesn't stick to galvanized surfaces and aluminium very well. Either get a specialist product, or apply self-etch first. No problems with it on regular prepared (roughened/cleaned) steel.

Cheers!

Willem Fick

Tim Hancock · 01-13-2005, 09:36 AM

Variprime is good stuff, it has a self etching component in it. I do not know if bondo can be applied directly over it (my GUESS, is that it would be ok). The metal prep I mention before applying epoxy, does the same thing as the etching component of Variprime. The epoxy (Dupont Corlar or PPG DP 40) is not cheap either but it seals better than Variprime. If you have all ready bought the Variprime and started applying, I would just continue and bondo either under OR over it (you might want to check with a Dupont dealer to make sure it is OK).

Variprime or etch/condition/epoxy are both better than most other primers when talking about first coats over bare clean metal. Niether are great for fill/sand before topcoat but it sounds like you have all-ready bought some primer to apply over your base primer that you can sand.

It sounds like you are way ahead of the average DIY painter. Just stick with one brand of products and ask your dealer for Data sheets on the products you are using. These "instructions" typically list what products will work over others and they give good prep and sandpaper grit reccomendations.

Good luck

Argeo · 01-13-2005, 09:46 AM

"It sounds like you are way ahead of the average DIY painter."

I wish, I am just lucky to have a friend that does this for a living. He's been talking me through the steps and what I need. The list is never ending. I just found out I need to drop another $100 for some coat that goes between the primer and the paint, something about getting the car uniform in color he said after the block sanding.

I was originally suppose to trailer over to him to have him do the finish paint but the cost would be too much to trailer. He's offered to come over and paint it at my house which is great and then talk me through the finishing steps. I had no idea it's about three days work after the paint goes on.

The paint is chromobase.

A lot of work ahead. Ugh.

Thanks,

David

Zeke · 01-13-2005, 09:47 AM

Good advice here from everyone so far. Let me add that some base primers are meant to be primed over if you intend to sand aggressively, as in block sanding. First off, you don't wnat to sand thru your base primer.

By the same token, you probably don't want to out bondo directly over a base primer. Bondo is made from polyester resin and so is polyester primer. A great marrige.

Here's what I do: after stripping the meatl and working out as much of the unevenness as I can with body tolls and heat, I put on some filler and sand straight. I finish that coat up with 180 or 220. I then prime with the base primer or go directly to poly primer if I'm not sealing the whole car.

I may need to work the area some more; at that point I use the ultra smooth filler. Reprime with poly primer, block again and ready the surface for paint with 400 grit. all the while trying not to sand all the way thru any of the base primer.

I'm a fan of sealer before painting. This is your final caot of "primer." You can actaully go over areas of different composition, as in poly primer, a little base primer peeking thru and a last minute touch up bare spot of the real fine finishing bondo.

Argeo · 01-13-2005, 09:54 AM

Thanks Zeke.

I got three different bondo's. In simple terms (the only way I get it) is the thick (Fiber glass resin) first coat, the second stuff which is more workable than the first and the last really fine stuff.

Sealer, that's the stuff.

well, I'll print all this stuff and get going.

Thanks.

David