Rain and Flash Rust

SMS

Promoted Users
My trailer project took a sucker punch last night. My 42' Chaparral got blasted over the weekend with Black Diamond abrasive. It has not rained in 6 week around here. Plan was to do some lead panel seam work and fill some pin holes today and clean and epoxy tomorrow as the forecast looked good for it. Painting outside.

But last night they were calling for rain so I put it under the mother of all tarps, and to keep the dew off of it. But the rain came as a severe storm with 35 mph wind and the tarp blew off. So now I have a nice layer of flash rust all over the freshly blasted steel. Looks to come off ok where dry with an 80 grit pass, but the rougher area pits get skipped over by the paper. Maybe a hand wire brush on those spots? Afraid to try Evaporust or similar product unless advised otherwise by you guys.

Thoughts?
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Barry

Paint Fanatic
Staff member
Dont like offering this advice as it can be taken the wrong way, so I want to clarify.

Flash rust only applies here, and flash rust shows up the next day over perfectly cleaned or blasted metal.
Here is why flash rust is different.
Flash rust does not hold air or moisture because of a lack of body-like pit, and scale rust does.
It easily sands off with a red scuff pad, unlike the other stages of rust.
Being you are sanding the flash rust off, a little left in a pit will be choked out by the epoxy as remember; epoxy is airtight and or waterproof.
Flash rust is different..
 

Toolin

Promoted Users
Flash rust only applies here, and flash rust shows up the next day over perfectly cleaned or blasted metal.
Here is why flash rust is different.
Flash rust does not hold air or moisture because of a lack of body-like pit, and scale rust does.
It easily sands off with a red scuff pad, unlike the other stages of rust.
Being you are sanding the flash rust off, a little left in a pit will be choked out by the epoxy as remember; epoxy is airtight and or waterproof.
Flash rust is different..
Thanks for the clarification.
 

crashtech

Combo Man & Mod
If we are receiving something that has been blasted, it's all hands on deck to put epoxy on it immediately. No planning on metal repair or anything like that. Reasons should be obvious at this point. Repair areas can be sanded or spot blasted to enable repairs while the rest of the vehicle is well protected.

I am wondering if more failures aren't caused by simple adherence to this rule: Bare metal must be primed immediately.

That's not to say Barry's rule doesn't apply, but you have to wonder about every hour that fresh blasted clean virgin metal sits there, what kind of contaminants can land on it that are way worse than a bit of flash rust. Anything that touches it can compromise adhesion.
 

LITJOHN

Promoted Users
The Chevelle I'm working on started out as a father / son project, not so much now....when we got the car we gutted the drive train, raised the body and pulled the frame out and then stripped it. Took all the frame parts to a blasting shop, then to a frame shop. As soon as we got it back we hit all the parts with sanders and grinders. Washed all of it, wipped it all down and shot it all in primer in one day, a very long day. Had no
problems with the frame parts. The body was another story, we were fighting flash rust, finger prints, critter tracks you name it until the parts were in primer. Of course the enviornment didn,t help at all either, pole barn. Pole barn is storage now and a home for critters...
 

SMS

Promoted Users
As tempting as using a chemical was, I managed to remove all the rust with sandpaper and muscle. The pits below the DA surface I hit with a spot blaster and Black Beauty. Three looong days of sanding. Whew. I see orange when I shut my eyes.

Shot white epoxy on the door and black epoxy on the steel sides and next day ran some 3M 2k 08308 seam sealer down the side panel joints. Ready for bodywork now and the weather tension is somewhat reduced. Thanks all for your advise on this project.
 

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SMS

Promoted Users
With the flash rust issue behind me, maybe I’ll post a restoration thread later but for now here is a quick update on my Chaparral trailer. After I got it in epoxy I set about getting the massive flat side pockets straightened out. Then shot it again this evening with more epoxy. There is so much square footage I’m thinking I’ll stay on this side until It’s in finish coat (SPI black SS) then jump to the left side which is already in epoxy. Then the inside is going white epoxy and white SS.
Here is a before and after on the body work. I could sure use a Dean Jenkins sanding block on this one..... ;)



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shine

Member
flash rust shows the metal is clean. the iron in your water will determine how heavy it is . my well water here has very little iron in it . i wash blasted cars with dawn soap and rinse well. i blow dry them with a leaf blower . if i get a lot of flash i just scuff it and go .
it's those damn little black pits that will bite you in the butt .
 

DzlFC

Promoted Users
flash rust shows the metal is clean. the iron in your water will determine how heavy it is . my well water here has very little iron in it . i wash blasted cars with dawn soap and rinse well. i blow dry them with a leaf blower . if i get a lot of flash i just scuff it and go .
it's those damn little black pits that will bite you in the butt .
It's so hot here that pressure washing/blasting bare metal leaves a second problem. Hard well water deposits are dried on literally in seconds. Gotta put the rig back in the shade and wipe the spots off.
 
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