flash rust after sandblasting tank

[mason79]

i bought a tank from ebay and the insides were unbeliveably spotless, however the outside was rusted ,chipped and slightly dented.

i took it to the sandblaster to ready for paint, nice job and the tank is solid,

now i have some flash rust inside the tank, (all surfaces)i don't know what they did at the blasters, if maybe they use water but the rust is there and it's gotta go.

does anyone know if i should just slosh some of that phosperic acid everyone is talking about and call it a day,

or do i really need to seal it, after all the tank was 27 years old and the inside was flawless, now this, the rust is not all that bad just the stuff like you get on the brake discs after you wash the car.

[Erik the Red]

I conditioned my tank (used Kreem) and noticed the rust as you describe after it only sits a short while after the first 'acid step'.

My take on it is that the moisture in the air reacts with the metal to cause that rust. I'd be willing to bet that at the factory they put a coating on there to prevent that. (Thus some tanks still okay after 27 years.) Then at the sandblasters they may have blasted the inside too which removed the coating?

I would say that you'll probably need to seal it to prevent it from getting worse. Kreem is some messy stuff and the acid will destroy painted surfaces if it's not wiped off immediately. And I mean IMMEDIATELY! That was my best option when I was looking. (Did this last summer, so can't comment on the longevity of the product... so far so good though.)

My $0.02.

[xschop]

rust

If your tank only rusted after this blast procedure, then the rust is only a few microns deep, ideal for the phosphoric acid treatment. With this small layer of rust, the h3po4 will leave a coating of iron phosphate(black) and essentially seal the metal... I would try that first, then coat it with Johnson's tank coat which will NOT come off like KREEM. I have a tank I just did this way....beautiful....chop

[mason79]

they did not blast the insides,

and yeah, the rust is just surface stuff

why don't they line the insides from the factory?

[Hobbit]

Why?

$

[Erik the Red]

Did a search for Johnson's tank coat and happened across the following forum. It may have a couple more ideas for dealing with a rusty tank for you too. Adventure Rider forum

Found some references to the Johnson's liner, but couldn't find any info on the product itself. Where can I find some?

[Dragonrider]

They don't line them from the factory because it's not necessary if you keep fuel in it and use it regularly.

I'd get her painted/etc, clean it with the acid wash, fill it up, and go!

I don't seal them unless they've been damaged (pitted/pinholed/etc).

Sealing is kind of a last resort. In the long run it will be more problematic.

[xschop]

this is the best I have seen/used

http://www.johnsonmfg.com/temp/FTOOL.HTM #238-01 will do 2 xs11 tanks!

[trbig]

Take some 2-stroke gas that has a little oil in it. Slosh it around in the tank and drain it out.. It will coat the inside with a light oil and fuel and stop the rusting for a while. I would repeat that a couple times until the gas was fairly clear... tape it off and paint it. Just use a cleaner if you get any of it on the prepped outside surface to remove any oil from there. Probably the easiest way. Once you keep it full of fuel you won't have a problem with it. The flash rust isn't really the problem, it's when you start getting the flakes of rust that it will start clogging things. Maybe even do a quick carb clean after a few tanks get put through it.

Good luck... and above all else... TAKE SOME PICTURES!!

Tod