How long does it take a bare tank to rust?

[Tyro]

I have been readin' up old threads and wiki regarding tank de rusting, and trying to decide which of the methods I'm going with.

Saturday is the monthly "Nasty Household Crap Drop-off Day" for my county. I'd like to drain the nasty old gas from my GS tank tomorrow so I can properly dispose of it. Unfortunately I have no POR15/Kreem/etc on hand. If I drain the gas then hit it with one of the hardware-store solutions (MKE/CLR/acid/?) will it stay good for the 7-10 days it will take me to get some POR-15 and have time to apply it? Or should I just wait and do it all within the span of 2 or 3 days.

Or can I just clean out the rust, do the H20+baking soda thing to neutralize it, then fill it up with fresh gas... I realize that the bare steel will eventually re-rust, but what kind of time frame is that? One season?

I live in a dismal swamp in Virginia, on a peninsula, 30 miles from the bay. It's humid and salty. Unrelated but the pollen is craptacular this time of year. My car is freakin' yellow and my eyes are killing me.

Thanks!

[GeeP]

Go ahead and drain the gas.  You will use Muriatic Acid to de-rust and etch the tank.  This can be washed down your drain or evaporated in the back yard.

If you want to do it tomorrow, go to NAPA and pick up a quart of Red Kote tank sealer.

The problem is that automotive fuels contain alcohol.  Alcohol attracts water.  Eventually, any tank will rust, even if it is kept full.  If you're going to go to the trouble of cleaning it out you might as well coat it.  The only downside to coating the tank is the possibility it might peel off at a later date.  Some say the tank coating is good forever, but my practical experience says around 5-7 years.  More if the tank is very clean and well etched.

[ducati_nolan]

If you're talking 7-10 days before you do your treatment, I wouldn't worry about it. You're going to clean out the rust anyways, and none to very little will form in a week or two.

If you're really paranoid about it, you could fill it up with gas and it wouldn't rust at all, or you could slosh a little WD-40 or other light oil in there too.

But I wouldn't worry about it. 

[MikeNW]

I am convinced of the merits of Marvel Mystery oil.  Especially for introducing some oil into these metal gas tanks.

[Tyro]

Thanks guys!

After checking a few, I eventually found a local (well, 25 miles isn't too far away) radiator shop that sells Red Kote and picked some up. This afternoon I drained the old gas (that took a while, there was about 3 gallons) and pulled the petcock and flippy lid thing off. Then I rinsed with H2O, drained, duct taped, and poured in a bottle of Naval Jelly. Sealed 'er up, shook it around every 10 minutes for about 45 minutes, then emptied it, rinsed 2x with hot water and baking soda, and one final rinse with cold water from the faucet.

It looks great! The rust is not 100% gone, more like 90-95% gone, but the difference is night and day. There are a few spots remaining, most are tiny and look very superficial now. The biggest one I can see is between dime and nickel sized. I doubt it would've hurt it at all to keep the acid in for another hour or so.

I stopped for the night because the sun was going down. Tank is sitting on cinder blocks in the living room with a fan running into it. Tomorrow comes the Red Kote process. How do you guys keep the petcock hole and 3 screw holes (one in bottom one on top of tank) from filling? I was thinking about sticking a Q-tip into each one before I tape it up...

[ducati_nolan]

Wow you have your gas tank sitting in your living room to dry overnight. I take it you're single 

Anyways, I'd put a couple of bolts through the petcock mounting holes to keep them from getting all gunked up. Just tape over the rest of the opening and you'll be able to clean up the opening after it dries.

[Nikolas]

I usually coat freshly cleaned tanks with 2-stroke oil.

[Tyro]

Nolan... yep just me and the dog. My girlfriend doesn't live with me and the roommate is away... 

I ran another thing of Naval Jelly this time diluted with water. Then after rinsing hit it with the MEK. It actually looks a good deal worse now.  Light orange rust over more of the tank and the areas that were rusty are now darker which I am assuming is the phosphate.