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Try http://www.evercoat.com/product-deta...art/100440/us/ it works, I used it in the same application you are doing its Evercoats pin hole eliminator, I also used epoxy as a sealer before final color.

Originally Posted by Bob Parmenter

Good thread.
Matthyj makes a good point about learning from someone with lots of positive experience. I learned about using phosphoric acid (in it's various forms/brands), as an example, years ago to kill rust from a guy who knew what he was doing. I read often online in various discussions about people who say you can't paint over steel that's been treated with phosphoric acid because it will "blow up". I take that to mean the top coat fails in some way. They may be correct..................in their situation. My guess would be they didn't do the full process or didn't do it correctly and left some residue behind. Cleanliness, make that absolute cleanliness, is the "secret" to good refinish outcomes.

Uncle Bob, I'd like to hear more about this phosphoric acid rust treatment, whether here or somewhere else if that's too much of a hijack for this thread. I have a few rust bubbles near the rain gutter on my '66 F100 that definitely need some attention. I'm hoping they won't require major surgery but in the meantime, an effective treatment would be helpful. Thanks!! Great thread, guys!

Originally Posted by 36 sedan

Dave,
AROC, check out the quote and thread link below;

Un-streetrodding a 34 tudor

I've been dealing with air pockets in the fiberglass by the hundreds. I often stick an Xacto knife tip into the hole and twist it around to see how deep it goes. Most of those are minor, compared to this. The defect goes around two corners at the top of the door openings and all the way around the trunk opening.

I'm now trying to figure out why my pictures don't display. I copy the same IMG info from photobucket, that I have in the past.

http://i1282.photobucket.com/albums/...psoeadwvfk.jpg

http://i1282.photobucket.com/albums/...psqqmtjydd.jpg

Originally Posted by randyr

Uncle Bob, I'd like to hear more about this phosphoric acid rust treatment, whether here or somewhere else if that's too much of a hijack for this thread. I have a few rust bubbles near the rain gutter on my '66 F100 that definitely need some attention. I'm hoping they won't require major surgery but in the meantime, an effective treatment would be helpful. Thanks!! Great thread, guys!

I have bought straight phosphoric acid from a chemical supply house in a gallon jug (actually a 75% solution), but it's available in a variety of smaller packaging, in lower strength from auto part stores, hardware stores, and paint suppliers. Navel Jelly is probably one of the better known retail brands. From automotive paint suppliers a common brand is Rust Mort. Most "rust retarders" available have some form of phosphoric acid as the primary ingredient along with dyes, thickeners, whatever else the seller feels will add difference/magic to their product.

The way I learned it is to apply to a rusty or non=rusty area very wet. If there is rust present scrape/wire brush off most of the scaly rust first. I will use a cheap brush to apply the acid, avoid "plastic" brushes, they dissolve quickly. Some will use a sprayer. I prefer the control of the brush. Depending on severity of the rust I'll let it sit for an hour or a few hours, just make sure it stays wet. Sometimes if the rust is stubborn (say in pits) I'll use a wetted wire brush or Scotchbrite pad (these get eaten up fairly quickly though). If you let it dry you'll have a hard, plastic like coating that is a mess from my point of view. If I brain fart and let that happen I sand that mess off and re-do. Once I've decided it's done its conversion thing (typically a dark black film look with some white foam or crystals about) to iron phosphate I'll give it a good washing with plenty of warm water to neutralize. That's the step that freaks out some people; "Won't that cause it to rust right away?" No, not if you've allowed sufficient time for the acid to do it's job. Below are some splash shields from my old Mopar that had just a slight amount of surface rust in a few spots. I blasted all of the old paint off and treated the entire piece(s). All these were done at the same time in the same way, the color differences I attribute to differences in alloy makeup of the steels used. Done this way it is an effective plating process (watch films of platers, they use various acids for a similar outcome).

I have done this sort of treatment on bare frames during construction where I don't want to have to grind away paint to weld on brackets or such. I've had a frame sit in the shop for a couple years (yeah, I'm slow) with no visible re-rusting. As long as the surface was cleaned of the acid residue thoroughly, and then re-cleaned as normal before spraying, paint sticks fine, probably better due to micro etching of the metal surface by the acid (which is one of the points of using Rust Mort as an example).

EDIT: just in case, it should be said, this is ACID, be sure to wear eye, lung, skin, and clothing protection during use.

Thanks, Uncle Bob!! That's good info right there!!

Ditto what he said good info Bob.

If you use POR 15 products, try Metal Ready, its a phosphoric acid based wash also. Something to keep in mind on pinholes, they are actually air "bubbles" meaning they are spherical in shape the pinhole is just the top of the sphere, like Dave mentioned they need opened up or filled by packing as the actual shape may be larger than what is seen.

Today, I gave the rear fenders 3 coats of epoxy primer (mixed up 22 ounces). I had more than enough so I did spot prime the running board, where I sanded through. Based on how it looked, the sealer coat alone would have done the trick. There was no evidence of the any transition between the old epoxy and exposed polyester primer.

I'm very happy with the sequence of scuffing the gel coat with 60-80 grit, applying and sanding filler as needed, then applying and blocking the high build polyester primer of your choice, followed by epoxy primer and more blocking. Scuffing the gel coat, followed by a high build primer isn't a bad idea either since minimizing the sand-through of gel coat will also minimize the exposure of pinholes in the base fiberglass. I now apply U-pol gold glaze to any area where I sand through the gel coat, because some pin holes will almost be a sure thing and they are hard to see in transparent fiberglass.

Evercoat has a new polyester primer that they call Finish Sand. It's a lot like Super Build, but thinner, with less orange peel and a not as much build-up. I probably wouldn't use Evercoat G2 again. The 4:1 products are easier to mix and sand a little better, plus they can be applied over bare metal, where G2 can't.

Evercoat Finish Sand 4:1 - 100738