Painting Over Existing Paint

[RodC]

I had this in Paint & Body but there seems to be more traffic here

I am in the middle of disassembling my bed to replace the wood and coat the frame with POR-15 The paint is in good condition with a few exceptions. Some chips and the fenders have the small flange rusting off in a few places. The truck looks like it was painted about 4 or 5 years ago. however they negelected to paint under the lip of bed and there is about 3 inches of surface rust on the bed sides.

The paint is not so bad that I would like to strip it but I want to paint the areas I fix and freshen up the rest of the paint to make it match. I plan on using Acrylic Enamel.

Heres my questions, If I paint over the existing paint, should I primer the whole panel, or just rough up the old paint?

What kind of primer should I use? Etch, Epoxy? Should I use the same on the bare places I Repair?

Thanks in advace, I have read so many confilcting reports, but we all know this is THE source!!!!

[Longhorn Man]

Personally, i would never paint over a repaint. I would only paint over a good original paint.
Not saying you need to take it down to bare metal, just at least run it to the first primer or first paint.

[mikep]

You really dont want to paint over the repaint without priming it first. Just a quick run of 400 grit should do it. Spray it with primer , wet sand and then paint it with your enamel. The primer you use is your choice. I usually use lacquer primer as it sands easier than catalyzed enamel primer and is easier to clean up and lay heavy fill coats with plus its a lot cheaper and you can thin with the cheapest lacquer thinner made without feeling bad. Figure half a gallon for a entire truck if you arent doing a lot of body work . Once cured you can top coat with enamel no problem. Lacquer primer is not for guys who like to drive around while still in primer though. Its good for a few months of summer weather tops. If you want to live in primer ( ugh ) then go catalyzed enamel primer ( its not really catalyzed but everyone calls it that ) or epoxy primer.

[Paul Clark]

Do you get any shrinkage with a primer that you thin with lacquer thinner?

[O'l Buck]

something you wanna be real careful of if you decide to go with a self-etching primer.......test it in a very inconspicuous area on your existing paint. I've seen it lift cheaper paints and it makes for a real nasty spider web looking patch which can be a real bear to get sanded off.

[basketcase]

I used to paint over a lot of different surfaces but occasionally that backfired. When I started painting other peoples stuff I stopped painting over repaints. You never know, unless you did it, what the prep work was on the last repaint. Lots of amatures or quicky shops don't properly clean or sand and scuff the old paint. You can lay down a coat of laquer primer ( which I like too) and it can lift the repaint like paint remover. With the cost of materials today I would never chance it.

Start by washing the bed areas to be painted down with Prep-Sol or other pre paint cleaner. Do this before you even touch it with sand paper so as not to work silicones and oils down into the sanded finish. Sand down to the original finish or to bare metal where you need to. Use an etching primer on all of the bare surfaces or the entire area if you want. Top that with a few heavy wet coats of the laquer primer so you will have something to sand to work towards that perfect surface. Be carefull not to break through to the bare metal. Apply more laquer primer as necessary to get the surface right.

Follow that with a sealer (probably a light color for your blue) and then the top coat of blue. Read the instructions for all of the products you are using and use the recommended solvents and follow directions for prep between coats.

Since you will have to remove the stepside fenders to paint the sides here is what I'm doing. I will take the rear fenders to a stripper (not that kind) and have them dipped to remove all paint and rust. Then I'll sand them and coat them with etching primer in and out. The insides will get a chassis black and the outside will get painted as above. Once installed I'll coat the insides with spray on bed liner. It will protect the fenders from rust and cushion against stones that make those little stars in the outer paint when they hit the inside of the fender. This is a good thing to do the the under side of the cab too.

Tom

[mikep]

Iv'e used the stuff since i learned bodywork 20+ years ago and have never had a shrinkage problem to speak of. Use fast thinner and it'll be dry to the touch almost as soon as it hits the surface and sandable within 10 minutes. 6 or 7 coats makes a good base for leveling slightly wavy panels and is dry within an hour or so. Block it with a long board or line sander and your'e done.

[RodC]

I was debating totaly stripping it, but it appears that it was. I can only find a layer of black primer and the layer of blue. Both are stuck pretty good. I'm still thinking, I have stripped a car with a sander and I don't think I'll go that route again!

Im thinking about having my tailgate and front panel sandblasted.