using old paint as primer

[crm318]

i have had thoughts about painting my ride myself. it is a 78 chevy van that i gave the 50 dollar rustolium paint job to. the paint looks good, but i want a better finish. the question is: will i be ok just sanding the rustolium (which is only a few months old) to a rough adhesive finsh and then paint over it with professional paint? i will be doing this with a paint gun and compressor.

[wibilly]

after just a couple months i doubt the rustoliem has even cured yet. i don't know for sure but i'd bewilling to bet that an automotive paint would wrinkel that rustoliem. you may get luckyif you sprayit in very light coats alowing plenty of time between the first couple coats but i would expect troubles

[72armyswbtruck]

Orange Peel city I would think, but I am very limited in my knowldege

[1bad chevy]

don't do it you need to sand the rustoleum off or it will cause problems

[19673ontree]

THIS IDEA WILL NOT WORK !
the problem is that the good paint that you will be putting over the rustoleum will LIFT it or unbond it if you will , if not for that it would work , paint's they make for car's now such as base clear are tough to spray over older paint's and even spraying them over themselve's before they have had a lot of dry time can lift , the best way to avoid problem's with paint is to remove all the old paint down to the metal and use a urethane 2 part primer , after that most anything you put over it will stay ,, I get beat up for it but stripping a car or truck to the metal is not hard at all and take's very little time or money , it's the cheapest and easiest thing you can do ,,
just use 36 grit sanding disc's on a 5'' or 6'' pad with an electric drill and get rid of all that old paint !!!
here is a pic if you have not seen it of how it look's after you get done ,,,

[N2TRUX]

Good paint is only as good as what it is put on. Please do not waste money on quality paint by putting it over poor quality materials.

If you want a nice paint job, you will have to have it stripped...

[crm318]

good call and thanks for the info guys. i will get to strippin!

[Mike 85]

carefull with the heavy grit paper cause you can "remove" more than paint. Namely,Body lines,edges,anything that "sticks up" and make low spots that you'll have to fill later by grinding too hard or long in 1 spot.
2K primer is NOT designed to go on BARE metal. Only epoxy or a DTM {direct to metal) or the crappy etch primer.Then,you apply your 2K primer.

[SactoJim]

Good rule of thumb is if it's a soluble product (non-catalyzed), get rid of it. Take a rag with laquer thinner on it and see if it removes any of the finish.....if it does, it is soluble.

When repainting over soluble products the solvent in the new coating will more than likely react with the older finish and cause a lot of "fun" problems.

Also remember that the adhesion of your new paint is only as good as what's underneath it.....meaning that most of these older trucks have had at least one repaint (maybe more if you're lucky) and you never know how it was prepped.

It's more work, but with what material costs are these days and time involved, I would feel more comfortable taking off as much of the old finish as possible, unless I absolutely felt that the existing substrate was sound.

[19673ontree]

Originally Posted by Mike 85

carefull with the heavy grit paper cause you can "remove" more than paint. Namely,Body lines,edges,anything that "sticks up" and make low spots that you'll have to fill later by grinding too hard or long in 1 spot.
2K primer is NOT designed to go on BARE metal. Only epoxy or a DTM {direct to metal) or the crappy etch primer.Then,you apply your 2K primer.

? 2K primer is not for bare metal ?
hum never heard that before , I was never able to get bodywork to hold until I started using the 2K primer over the bare metal , did my 67 camaro like that in 99 and with one job on it I took two left front fender's and welded them together to make one good one and put 2K primer over the bare metal then did the finish work , you still can't tell the repair was made and it's an 8 year old repair , my 67 C10 was just painted last year and it was stripped clean to bare shiny metal then 2K primer was sprayed over the bare metal , have not had a problem ?
? why can't you use 2K primer over bare metal ? just wondering ?

the 2K primer is activated by the hardener and once cured it is a permanent product ideal for use over bare metal . you can put spot putty and bodyfiller over it with better adhesion than bare metal ,,,,,

[SactoJim]

There are many things you can "get away with" when refinishing a vehicle as there are many different ways of accomplishing the same task.

On repairs where there isn't much exposed bare metal, you can get away with using just a 2K primer, but it's alway best to use a product that etches or is designed to go over bare metal.

If you had a completely stripped vehicle (bare metal) or larger areas of exposed metal I would definately use one of those products. (polyester primer, epoxy, DTM products, etch coatings)

you may "get away" with using something else, but if you do have a problem, it will be a time consuming, expensive mess to fix. Sometimes it takes years for paint problems to surface.

[19673ontree]

good point's .

back in the early 80's when just using laquer primer I had problems that showed up in week's !! not year's , today's paint's are much tougher ,

[SactoJim]

That's what I learned with....Laquer.....back in the day when materials to paint a car were less than $150!!!!

[impala_631]

i always like to epoxy first then 2k, but i guess you could go strait to 2k if you done have any problems

[Mike 85]

Read ANY paint manuf's tech sheets or ask a rep and you will find that a proper primer is required for proper adhesion of the following layers.
epoxy is the ONLY initial primer that inhibits corrosion and is a solvent proof barrier for using as a sealer over existing paint.
2K primer will 'work' over bare metal as you have seen but it is not DESIGNED for this,regular base paint will stick to bare metal also but it's not something you'd WANT to do.the 2K will stick over a good scratch and clean metal but applied over a smooth or dirty surface,it will come loose.
2K primer offers no corrosion protection,same for etch and "if' the OEM's would have had epoxy to use back in the day,we would not have all the 'fun' today of replacing all the rusted out metal.

[19673ontree]

I have used epoxy too , my problem with it is that you can't sand it , it is tough stuff though ,,,

[Mike 85]

Try some Southern Polyurethanes epoxy.
ONLY epoxy I use and it sands like 2K.
After 24,it is a little gummy in cool weather,but after you break the "skin",it sands smooth and no clogging of the paper. ANY epoxy after several months or so will be HELL to sand. Thats the whole idea. I have some fenders I shot last year I finally got around to working on and even using hammer & dolly work on them has NOT even thought about breaking thru it.

[crm318]

what about putting primer over the sanded rustolium?