Body / Glass: Spray can primers

[dstude]

I have some small body, dash and trim parts that need to be repainted. Some will have to have the paint stripped, others just sanded. Since the work will be done over a period of time, what spray can primers are people having great luck with as far as it adhering to the metal and not causing problems when it's time to paint the finished part? More important, what are the spray can primers to avoid; the ones that don't stick and have to be removed before final painting? Thanks.

[jnormanh]

I have some small body, dash and trim parts that need to be repainted. Some will have to have the paint stripped, others just sanded. Since the work will be done over a period of time, what spray can primers are people having great luck with as far as it adhering to the metal and not causing problems when it's time to paint the finished part? More important, what are the spray can primers to avoid; the ones that don't stick and have to be removed before final painting? Thanks.

I've used Rust Oleum aerosol primer under acrylic/urethane auto paint with good results.

[RadioRoy]

Be aware that many primers do not seal the metal. If things are sanded and primed, they should be painted. Otherwise rust will form under the paint.

[rockne10]

I believe any surface, even bare metal, is going to need sanded to provide some 'tooth' for the primer to adhere; and that primer is also going to need a sanding to get any final paint to adhere.

[Colgate Studebaker]

I've had very good luck with Duplicolor self etching primer. As others have said the surface needs to be "roughed up" before applying, and before the final paint is applied the primer should also be "roughed up". Bill

[Mike Van Veghten]

What Colgate said.
Very good stuff. It actually seals, most others do not.

Mike

[jclary]

For backyard/garage hobby work I would say just a light dusting of primer would work until you are definitely seriously ready to paint & finish your workpiece(s). The main purpose of the primer is to promote adhesion/bonding. If you know exactly what finish you are going to use, consult with that brand's representative for a compatible primer. If you do use a cheap rattle can primer and doubt its compatibility...a light dusting should be easily removed for the serious priming.

What I have found is that such parts left in a reasonably dry place will even benefit from being covered in shop dust. The dust will serve as a protective coating that will flash off any humidity that would otherwise settle onto the bare metal. So, if you are working, sanding, and get called away while the part is down to bare metal and you have no time to cover it with primer...don't panic, just don't wipe off the sanding dust. Leave it covered with the sanding dust and place it in a dry spot 'till you can get back to it. By the way, you are in California...nothing rusts in California...it just gets weird!

[wdills]

I have been using SEM self etch for years for small touch-up as well as small parts where I don't want to bother with setting the gun up. I have never had a compatibility problem between the SEM primer and anything I have sprayed it over, or anything I sprayed over it. The down side is you either have to order it online or go to an auto body paint store to get it. I have never seen it at a home improvement or typical auto parts store. Even though it is a self etch primer I still always sand or sandblast the metal to create some tooth.

[wittsend]

I have a car that had pock mark rust on the roof. I completely striped/sanded the roof of paint, and used copious amounts of phosphoric acid until there were no visible signs of rust present. The image is to illustrate I was not painting over rust. In fact I did far more prep work (sanding/application of phosphoric acid then is shown here).

I then painted the roof with three coats of 2K Epoxy Primer/Sealer (PCL 6701 A&B). While not garaged I did park the car beneath a drive under car cover in "sunny" southern California. Within 6 months there were signs of rust appearing. So, neither extensive prep work, 2K Epoxy primer/sealer nor California weather seemed to stop the rust of a car parked under a cover.

[studegary]

I consider all primers to be for temporary final coverage. Most, if not all, primers are porous and allow rust to start/progress.

[Lynn]

I don't believe any primer has UV protection. That means it will degrade quickly if not top coated.

[bensherb]

By the way, you are in California...nothing rusts in California...it just gets weird!

Sounds like something someone who's never been to California would say. At 80% humidity everything rusts here, even when it's 80 degrees like it was two days ago.

I use Rustoleum, "Rusty metal primer" it's a red/brown primer that is also a sealer. It will keep out rust for years, but, after twenty years you will have surface rust under it and showing through it, just as you will from plain primer in less than a year. Oh, that car has also been parked outside in the rain and in full sun at 105 degree temps for 20 years. Parts, I sand blasted and used it on that have been stored indoors for ten years are exactly as when they were sprayed. I've painted Imron, Deltron, Centari, Lucite and several other paints over it with no problems. I do scuff it before painting over it.

Oh yea! Don your pattern is in the mail. Hope it works out for you.

[Reggie]

For small steel parts that I've taken to bare metal, I use Rustoleum "Self-etching Primer" in an aerosol can. It dries fairly quickly & I advise that you go very lightly; no piling on of coats, and be sure you let it dry before applying top coats.. It's widely available, wherever Rustoleum paints are sold. Price is something like $5.75 a can.

[hank63]

For what it is worth - In industrial painting in Aus, clean blasted surfaces must be covered with primer inside 4 hours to minimise chance of microscopic rust forming. Single pack primers are slightly hygroscopic and are usually top coated within 24 hours. 2-pack primers form a barrier that moisture can't penetrate in a hurry, so the re-coating window is a bit longer. Note that DFT (dry film thickness) is very important, always ensure the paint manufacturer's instructions are followed.

[jimmijim8]

Clean,sand, or whatever your method of prep you do to your metal. Not advisable to paint over rust. Use rustoleum rattle can automotive primer usually less than 6 bucks. If you are going to be days or months away from top coat you might try storing parts in plastic bags.