Paint under rust?

B

Beauford

Well-known member
So utilizing my time while I save or fix non cooling radiator I did a little sanding on a door. I was noticing a little drag and thought maybe body filler. Lifted sander and it was blue. Is it possible under all this surface rust to have paint???
 

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Years ago, I had some rust fixed and only had primer put on (No money to get it painted).
After several months, I could see rust color showing up again in the primer... took it back and was told that primer is NOT a final finish since it is porous and will rust again.
Lesson learned!
 
After the sheet metal has been stripped, I etch the metal first with a metal etch to kill any rust. Following that I use a sealer over the bare metal to prevent any interaction between the sheet metal and anything that may be applied over it, including primer. As you have read above, using primer first over a car's sheet metal just isn't proper. Moisture can wick through the primer and attack the metal. I have also found that using a sealer over your completed body work (including the primer), you will get a much more even final color and more even "flow" to the paint that you have applied. Always make sure that your primers are completely free of moisture and solvents before applying any sealers/color over the primer. In 1963, having my car sitting out over night, it had collected dew. We didn't give it enough time for the body to warm up before putting final color over the primer. The first freeze that we experience, popped the paint like a rash on all of the horizontal (dewed) surfaces.
 
Steamer, what sealer do you recommend? This is going to be a here and there project with all the rust I need to sand off and I figure each panel I will use Phosphoric acid to prevent flash but I would like to use a sealer after it is complete.
 
In my shop, I use all Nason products. What ever your parts house brand is, use all the same brand products and do not mix between different brand names. Through the years, I have used about ten different paint manufacturers. They are all good brands and they all have comparable products to Nason. Follow their directions to the letter when mixing paints and don't forget to use a fresh air mask when spraying paints with hardeners. Even my modern sandable primer has a hardener added to it now. Not like in the 60's when there weren't hardeners or fresh air masks to use. The first coat after the phosphoric acid actually is a non sanding primer. Above I had referred to it as a sealer, which it actually is. It has a color to it, several choices of color available too. The sealer I put over my finished body work before your color coat is applied is actually a "clear" sealer. Amazingly, I can do a whole car with a quart of clear sealer and still have some left over. A professional body man, which I am not, would have more current answers to your questions. I am just an old fart car hobbyist.
 
The best product to put on bare metal is an epoxy primer. It has maximum adhesion and corrosion protection built into it. It can sit outside for 6 months and rust will not form. I have parts that I put epoxy on 20 years ago that have sat inside where it was dry and warm and there is no rust when you sand off the epoxy.
John Poole
 
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