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I have had my truck blasted and the guy primed it with an epoxy primer. I feel like that is all good. With my limited knowledge of body work, in an attempt to sand some bondo smooth, I have sanded down to bare metal in some areas. I went back and touched these areas up with a spray can of self etching primer from NAPA. I hope this will be ok? I have a gallon of a high build primer but the weather conditions or some other obstacle has prevented me from using it.
Also what is the best sandpaper for dry sanding bondo and what grits should i get? I have 80 and 180 already, although not enough. Has anyone found a place to get good sandpaper in 50 or 100 sheet packs?
Thanks tom
 

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The epoxy sealer is just that, a sealer. Depending on what they used for a blasting media, sand vs. soda, etc., the pores of the metal will be wide open with sand and in a much more closed state with soda or plastic media. The epoxy sealer seals the pores of the metal up so that the moisture in the air doesn't start the rusting process all over again. So sealer is a good thing in most cases.
When you sand through the sealer you are reopening the pores in the metal and re priming is always a good idea. Self etching primer sticks a lot better than the other primers if you are using spray cans to spot prime.
The high build should go on before color coat, but you will have to sand the high build to get rid of any sanding scratches left from previous work.
Hot Rod magazine just finished a series of articles as did Popular Hot
Rodding on body work - they would be a good guide to follow and may be available on their websites.
As far as sandpaper goes, go back to the NAPA store that sells the self etching primer and make friends with the guy behind the counter. Tell him what you are doing and what kind of tools you have available. He should be able to fix you up with what ever size, grit and method of connection that you want. Start with the lower numbers to grind and go up to sand and finally on to the three and four digit numbers to finish and polish.
I usually use only up to 600 wet paper, even with a DA sander, on primer, and block with up to 1000 grit after a guide coat on the primer. I don't color sand the color, only the clear. I start with 1000 and work up to 4000 depending on what I want the thing to look like and how bored I get with the polisher.
Good luck.
The Oldstreetrodder
 
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