700 causing flash rust on bare metal

Lizer

Lizer

Mad Scientist
Several times now I have been getting flash rust on bare metal immediately after cleaning with 700. It's been frustrating to the point that I've stopped using it on bare metal despite best practice and started using 710.

I don't recall this always happening with 700, especially when it was still alcohol-based. Stupid EPA.

Does anybody else see this or is my jug going south?
 
the 700 is alcohol and water and of course if that hits metal then sure it can flash rust but if your wiping down to shoot epoxy within maybe 30-60 minutes, whay does it matter? i cant paint any steel here in the summer without spraying epoxy over flash rust. metal here will flash rust faster then i can blast. it will not come back to haunt you. as long as you have the old rust off and out of the pits then your fine. with that said it could very well just be the 700 your seeing on the rag.
 
Yes, flash rust is to be expected from what ever the moisture in the air may be that day regardless of the wax and greaser remover base chosen. The choice of wax and grease remover should not be not much of a concern on a warm day with fast flash-off of either. Rust (FE2O3) is the by "by-product" of the aqueous corrosion FEOH- attack on the steel's surface and not the problem. The OH- attack is the problem. Flash rust will form even for a brief period with high humidity sometimes in five minutes or less. Neutralize the basic attack (OH-)with a with a quick low molarity acid wipe and flush the residue and any precipitated salt off with a garden hose rinse if it is a bothersome concern. I won't bother--but I would blow dry with warm air or get a heat lamp over it for a brief artificial surface dry time and scuff with a grey scotch-brite, especially if it is a large flat surface. Or a large CFM fan over the item will help drive off moisture less effectively.
 
D.A.T. said:
Yes, flash rust is to be expected from what ever the moisture in the air may be that day regardless of the wax and greaser remover base chosen. The choice of wax and grease remover should not be not much of a concern on a warm day with fast flash-off of either. Rust (FE2O3) is the by "by-product" of the aqueous corrosion FEOH- attack on the steel's surface and not the problem. The OH- attack is the problem. Flash rust will form even for a brief period with high humidity sometimes in five minutes or less. Neutralize the basic attack (OH-)with a with a quick low molarity acid wipe and flush the residue and any precipitated salt off with a garden hose rinse if it is a bothersome concern. I won't bother--but I would blow dry with warm air or get a heat lamp over it for a brief artificial surface dry time and scuff with a grey scotch-brite, especially if it is a large flat surface. Or a large CFM fan over the item will help drive off moisture less effectively.
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No, it only flash rusts with waterborne, not solvent. In SW MI it is not very humid. I can have blasted parts sit for years without getting any substantial rust.
 
Jim C said:
the 700 is alcohol and water and of course if that hits metal then sure it can flash rust but if your wiping down to shoot epoxy within maybe 30-60 minutes, whay does it matter? i cant paint any steel here in the summer without spraying epoxy over flash rust. metal here will flash rust faster then i can blast. it will not come back to haunt you. as long as you have the old rust off and out of the pits then your fine. with that said it could very well just be the 700 your seeing on the rag.
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I don’t think it’s alcohol anymore. He had to take that out several years ago. Now it’s ammonia based.

//edit: it still is alcohol based, but Barry said the alcohol should work as a rust retarder if anything.
 
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We go through quite a bit of 700 and it never has a chance to turn brown. It seems kind of odd if you are using gallons of epoxy (I recall this from a different thread) that your 700 would have time to turn brown. I guess I might dump it out and start fresh even though it's supposed to be okay.
 
crashtech said:
We go through quite a bit of 700 and it never has a chance to turn brown. It seems kind of odd if you are using gallons of epoxy (I recall this from a different thread) that your 700 would have time to turn brown. I guess I might dump it out and start fresh even though it's supposed to be okay.
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If I recall it has always kind of been brown. Barry said the color was fine though.
 
Well as Jim says, a little flash rust just means the metal is super clean and reactive. Maybe do smaller areas so the surface is wet for less time, and just get the epoxy on asap. I still think 700 is best no matter what, the tech manual agrees, if I'm not mistaken.

Our 700 is never brown, it's very slightly yellow.
 
So to answer your previous question Crash, most of that epoxy has been going onto a 28’ camper I just finished painting for a friend. He’s been doing all the prep work and I bought this gallon for him last year. He’s used most of the gallon cleaning it. He did a wash step with Dawn first. But then two coats of epoxy on a 28’ Argosy (basically a painted Airstream) eats a lot of epoxy.

At any rate, I talked to Barry earlier today and he confirmed the color isn’t problematic, that there’s nothing wrong with it and that he does hear this sometimes and doesn’t know exactly why it happens other than it’s seen on certain metals/steel.
 
I am wondering, for those who hang onto a gallon of 700 for a long time, if it wouldn't help to decant the gallon into smaller containers. I would be bothered if our 700 turned brown even if it's supposed to be okay. It was more of a problem many years ago, iirc, and I thought something had been changed to reduce that tendency. It's certainly not been a problem for us, at all.
 
crashtech said:
I am wondering, for those who hang onto a gallon of 700 for a long time, if it wouldn't help to decant the gallon into smaller containers. I would be bothered if our 700 turned brown even if it's supposed to be okay. It was more of a problem many years ago, iirc, and I thought something had been changed to reduce that tendency. It's certainly not been a problem for us, at all.
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It was more of a problem years ago and the only reason Barry said he changed it is because people would complain on the forum about it changoing color, even though the color change had no effect on performance whatsoever. It was purely an aesthetic thing.
 
Lizer said:
I don’t think it’s alcohol anymore. He had to take that out several years ago. Now it’s ammonia based.

//edit: it still is alcohol based, but Barry said the alcohol should work as a rust retarder if anything.
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Water is miscible in alcohol like copper is completely dissolvable in gold. Known as binary solubility. You will simply have a solution--not two phases and no rust prevention or tendency to go OH- with the alcohol and cause corrosion. The more polished or stressed the surface on a sheet of steel from blasting or fine grit sanding--the faster it happens.
 
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