I guess it depends on what they dip it in. I'm assuming it wasn't sheep dip, but paint remover and/or maybe rust converter.

I have not heard of dipping, but if it's just to remove the paint, I would assume you need to primer it. Don't know about sanding. If they use ospho (phosphoric acid) in the dip, you need to be aware of that, as it's not compatible with epoxy primer.

I'm sure someone will weigh in with more info, but you should quiz the guys who're doing the dipping to find out what they recommend.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.