Topic: Yet another gas tank rust question.....

[Chad]

My tank had some minor rust when I got it and was causing problems with my carbs so I decided to clean it out. I did lots of research on this site and found several solutions. I have tried The Works and Phosphoric Acid. Both worked amazingly well at removing the rust from the inside of the tank.

The problem I am having is flash rust afterwards. Here's what I've tried:

• Baking Soda rinse after using the acid
• Baking Soda rinse and then drying out with hair dryer
• Putting in marvel mystery oil after soda rinse
• Also tried ATF and 2-stroke oil after soda rinse

No matter what I do, the rust comes back. I don't have much of a budget so I have been trying to avoid the POR15 kit. Is that my only option? Has anyone else ran into this problem?

Thanks!

[lone*X]

Lets assuming you got all the acid out.  It takes Oxygen for rust to form.  You need to exclude the oxygen by some means.  You do have the cap installed with a good rubber gasket, right?  A well oiled surface will exclude the air for storage of an empty tank but the oil has to stick.  I imagine MMO is too thin to cling to the metal surface for long.  I have a tank that has been stored for three years after it was cleaned with just a couple of quarts of 30wt. in it with no new rust.  I check it ever few months and roll it around to make sure the oil has completely re-coated the inside.

I am going to guess that you are not getting it completely dry either.  You may think it is completely dry but water will get into the seams around the bottom and you don't see it.   A hair dryer may not evaporate it all out.   As it eventually evaporates it adds humidity to the inside of the tank.  You can remove all the water by a good rinse with straight denatured alcohol.  The water will mix with the alcohol and after you pour it off the alcohol will evaporate taking the water with it.   Then is the time to protect and seal the tank.

[BeSeeingYou]

I don't think you should use the baking soda rinse with the phosphoric acid.  Any other acid yes but phosphoric is meant to dry in the tank and leave a protective coating.  just wrap a rag around a coat hanger and use it to soak up the small amount that is always left in the tank so you don't have a puddle that dries and leaves a white powdery residue.

[dougan]

I've done this with two 2-stroke mopeds and both ended up great.  I used vinegar for both, and I had to let it sit for a week.

After I drained the vinegar, I washed it very good with soapy water, shook them out the best I could, sprayed a bunch of WD-40 and Fogging oil in there (which probably did nothing), and then immediately filled it to the top with mixed gas and never had any problems.  I think the oil in the gas helped out a ton, but, looks like you already added straight oil.

Maybe it's because you used a really strong acid?  I chose vinegar because it was way less strong than The Works.  It takes way longer, but the result I got was still awesome, even though it took a week.

[lucky]

You cannot just clean it and refill with gas anymore.
The gas now has 10% ethanol which attracts water.
The tank needs to be sealed.

If you take a brand new steel aftermarket gas tank and fill it with gas and you do not treat the inside of the tank within one month the tank will be all rusted.

[BeSeeingYou]

You cannot just clean it and refill with gas anymore.
The gas now has 10% ethanol which attracts water.
The tank needs to be sealed.

If you take a brand new steel aftermarket gas tank and fill it with gas and you do not treat the inside of the tank within one month the tank will be all rusted.

I don't think so.  Four years ago I bought my F1 that had been sitting for 25 years.  The tank had some minor corrosion and lots of gas varnish.  After cleaning out all the corrosion and varnish I did NOT seal/line the tank and the whole inside looks just as clean as this four years later.  And plenty of 10% ethanol has run through this bike....yeah not the best thing but sometimes when you need gas it's all you can find around here.  I drain my tanks and store them inside over the winter and that helps too but even my 79 XS650 has never had a serious corrosion problem in an unlined tank and I have run that bike for 32 years.  I finally gave it an acid bath a few years ago to clean out some minor corrosion maybe covering 5% of the inside of the tank. 

[Retro Rocket]

Besides, Tank liners suck, never used one and never will. {yes we have ethanol}