Hi, I know primer isn't water proof over long periods. My question is, if I wet sand with 360 grit and don't reprime, will that make it less water proof ? I think I read somewhere about it breaking the seal when you sand it, if that makes sense. Thanks.
I think it probably breaks the surface. It probably depends on how long its been on there and if its done gassing out yet. If its not done gassing out it should seal itself back up wel as sealed up as its going to get.
I dont know what primer is on it, you can tell its been primed a few times and the last time was shot real dry, very rough, don't know how long ago. The last time I painted was in the 80's with lacquer paint. Dont know how its done with newer paints, but we used 150 grit then water sanded with 360 and reprimed - resanded ect. until straight, color sanded with 1000 or 1200. Just got this as a new project, working on geting a compressor, but it might be awhile. Just wanted to do something to it and starting the sanding was the best thing I could think of. The truck does sit outside, the garage is full.
If you sand you break what little "seal" there is. Most primers, urethane or lacquer based, are essentially talc suspended in whatever base is used. 2 options as I see it, sand it and reprime with a good urethane primer or leave it until you can. Epoxy primers have much less solids employed than surfacing primers and depend on a specific curing time or process (like heat). Still, once sanded any water-resistant feature is reduced. Primer will survive wet sanding because it's not left to soak for hours at a time and is constantly dried to check the work...unless it's Kondar by PPG. That shit will suck water like a sponge and surface rust the bare metal below. Don't ask me how I know. I'm almost over it (20+yrs ago!).
I talked to the guy I got the truck from, he didn't remember the brand but said it was a mid priced self etching primer shot about 3 years ago and kept inside. I'm thinking about getting a tp tools turbine hvlp since I'm doing this in the driveway, not going for allout show paint, just trying to get some color on it. Should I go with laquer or try the newer paints? I'm thinking a solid two tone white and blue, looking for the easiest thing to shoot as this will be my 1st paint job in over 20 years. thanks.
Here's an example of what Highlander is referring to in terms of moisture absorption. I just re-stripped this spare fender after originally sanding down to bare metal about 45 years ago, and used Rustoleum, as I recall. It has been in DRY storage ever since; hard to believe.......Hope the rest of the body has not been affected as badly!!
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