The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by Shakedown St., Sep 22, 2017.
After sandblasting a frame, is there anything you should coat the exposed metal with?
I have done several with POR15 ,,,,,great results
Lotta air to get rid of the excess sand....then you need to wipe it down with your favorite brew to get oils/contaminates and such out/off of it...now you have clean, ready to work with bare metal...treat as you would a door, fenders, car, etc....really depends on how soon you are going to act on it...if this is a weekend project just grab your primer and paint and go, will probably outlast both of us...if the frame is gonna sit for a week/month etc...then that changes the way to approach it.
I'm one of those impatient bastards when it comes to a frame...shoot my cheap primer, semi gloss black..and be done with it, then again I don't build show cars...do you?
And within 8 hours of the blasting operation.
Can you buy epoxy primer in a spray can or does it only come for use in spray guns?
Yup, but I have never used it. Not sure how good it is.
I am not a fan of por15, its a lazy mans way to paint a rusty frame. Have you ever tried working on a frame that's been painted with it? You can't get that shit off to weld. If it's already sandblasted, epoxy primer and a coat of good enamel with hardener.
Use long lasting POWDER COATING!!!!!
After sandblasting I wipe the entire frame down with a final prep cleaner,to remove the excess residue.
In my way of thinking the primer depends on the car I am building,in this case it's the frame under the '54 Ranch Wagon and basically none of it would show unless it's on a rack and the car was built to drive,not show so I actually brushed on a slightly thinner coat of Rustoleum red oxide primer.
After it had dried I painted it with semi-gloss industrial enamel black,I brushed it also.
It has held up well. HRP
I first used etching primer and within 3-months I could see rust coming through. I had to re-blast and paint it with Epoxy primer stored the frame for 2-years with no sign of rust. Use Epoxy primer !!
i agree on the painting over rust being for " lazy men" I do not advocate that,HOWEVER moisture cure urethane is the toughest most durable finish I have ever seen, I have used it straight over sandblasted frames, axles,transmissions etc.and it appears indestructible!...as far as welding I sand it off with a " flapper disc" to bare metal, put a clean new disc on and hit it one more " quickie and weld.....but I am just building " nice" driver quality not show car stuff
Eastwood sells epoxy primer in spray cans also.
I was taught epoxy primer has to be a two part mixture and must sit for 1/2 hour after mixing to get the desired chemical reaction. Then stir again before application. I would not believe a one-part product is epoxy just because the label says so. I had used mil spec epoxy primer for many years while in the military, highly recommended, excellent results. After application you must topcoat within a certain amount of time or you will have to scuff sand before doing so. Whatever you use, do NOT let that freshly blasted metal sit uncoated for any longer than it has to. It will flash rust before you can get back from the paint store.
As far as etching primer, I used it once a while ago. It did ok but the car has not left the garage since. In my opinion, an etch is a separate operation and not even needed on metal that has just been sandblasted / roughened.
You guys who say you need to paint within hours must live underwater. I live in humid Iowa, and have parts that were blasted years (maybe even ten) ago that are still bare clean. Maybe a fingerprint of rust where I picked it up with sweaty hands once.
You need to shoot a good two component epoxy like PPG's DPLF or DPLV. That's the only right way to seal the bare steel. Etching primers are 1K acid-activated and can be reflowed with aggressive chemicals. Etch's can't be topcoated directly, and don't like a rough profile like sandblasted steel. DP Epoxy and a coat of a single stage black urethane or enamel over it and that frame will last 100 years...
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Yes, I think etching primers are more suited for chemical dipped steel and soda blasting.
A friend told me he had a car soda blasted years ago and said he had a hard time with paint adhesion.
I apply a good amount of Metal Prep to any bare metal. It's a phosphate based solution, which is what the OEMs use for rust prevention.
Lately, I've been using a high zinc spray primer over that "prepped" metal. It mimics the properties of galvanized metal.
Then you can lay down your chassis black.
The OEMs figured this out decades ago.
Singlefinger Speed Shop,
still lurking around Detroit
I'm certainly no expert on paint or primers. I trucked my bare frame home from the sandblasters and shot it with etching primer 9 years ago. It's in a damp garage and hasn't rusted yet. The etching primer grinds off easily to weld but when it gots hot, it sends off nasty fumes! I'll do my finish welding and shoot it with a good primer and then paint.
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