Wet sanding primer

[VW1300_1974]

I've painted the rear valance of my Beetle in filler primer. It needs sanding, as it's a little rough in places, before I spray the top coat. As primer is porous, if I wet sand it will this encourage rust to form under the primer?

Any advice would be much apreciated?

[marklaken]

what brand/product name of primer?...i think you are okay if it was a two part catalysed primer to wet sand all you want...
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Mark Laken
Fort Collins, CO

[VW1300_1974]

It's Silkens (spelling?) cellulose high build primer, I think?

I'm a home restorer and the paint was supplied by a mechanic friend who borrowed it from work .

I've just read a lot of topics saying primer is porous and rust will develop if left unpainted. Then they go and talk about 'wet sanding' it. Surely this is a bit of a contradiction?

[Obsessed]

wet sanding is not required. I like to use 320 paper before spraying the base coat. remember, the paint bonding to the primer is a mechanical bond, not a chemical bond as with the top coat. you want to have some "teeth" for the paint to grab onto. I know people who wet sand the primer with no problems, but I don't recommend going any finer than 400.
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[bmtx]

320 dry or 600 wet. Wet sanding isn't nessecary but it is cleaner and smoother than dry sanding.

[Teeroy]

Wet sanding is fine , just wipe it dry when you are done . What final grit paper is determined by what you apply next . If sealing then top coating , or if top coating directly over the filler primer . The best thing to do is read the tech sheets for the paint line you are going to use , they have all the info (temps , sanding grits required , dry time , what can be applied over/under what) . Try using the same brand/line from start to finish also , better results and less chance of problems . TROY
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[VW1300_1974]

Thanks guys that's alll very helpfull.

I'll get sanding!