Topic: Gas tank Derusting

[fendersrule]

I plan on using the vinegar method since my tank only has light rust.

Then, I'd do a good amount of rinsing afterwords.

but how exactly do you "oil it up" inside to prevent flash rusting? Let me know your exact process, because I'm going to have to do it soon!

[Terry in Australia]

Once you've rinsed the tank thoroughly, dry it out as best you're able (a litle methylated spirits tipped in and swished around will help) then once its dry, a small amount of a thin oil (two stroke oil, ATF etc) tipped in and swished around will prevent it from further rusting, and won't hurt your engine. Cheers, Terry.

[fendersrule]

How much is a small amount? a half of a cup?

It seems that even with a half of a cup, there is no way that you're going to get oil to cover all of the steel in a '78 CB750 gas tank. There are so many baffles/reservoirs that I would be doubtful. But I could be wrong.

[Cqyqte]

I spray the inside surface of the vinegar cleaned tank with a can of "Fogger" an marine engine winter prep product (oil and rust inhititors).  Works great and doesn't mess up the carbs.

[Terry in Australia]

How much is a small amount? a half of a cup?

It seems that even with a half of a cup, there is no way that you're going to get oil to cover all of the steel in a '78 CB750 gas tank. There are so many baffles/reservoirs that I would be doubtful. But I could be wrong.

Yeah mate, you're wrong. There are no baffles in any CB750 tanks (I've cut them all open at one time or another) so tip in a cupfull of two stroke oil or ATF, swish it around thoroughly, and it'll coat every nook and cranny in your tank, then just drain off the excess. The other benefit is the oily fumes will fog your exhaust system with an oily mist, preventing it from rusting out. Cheers, Terry.

[MJL]

Once you've rinsed the tank thoroughly, dry it out as best you're able (a litle methylated spirits tipped in and swished around will help) then once its dry, a small amount of a thin oil (two stroke oil, ATF etc) tipped in and swished around will prevent it from further rusting, and won't hurt your engine. Cheers, Terry.

When I fixed my oil tank I put water in to make sure it didn't leak, then put it in the oven at 250 for awhile to evaporate the water.

[CROMOLY]

So, ultimately, I was using the Evapo-rust and the tank was coming out great. And I have come to several conclusions concerning the pros and cons of it and vinegar.

Vinegar PROS- It's pretty cheap. You could fill an entire 5 gallon tank for around $5 or $10 bucks. This makes it pretty easy to just fill it and let it sit.

Vinegar CONS- It seems to take a looooong time and isn't as effective on the heavily rusted areas. These required scraping eventually and later some wire brushing.  The main reason I don't like to use vinegar (I was quickly reminded) is the smell. The process smells like rotten eggs. It stunk my whole apartment up.

Evapo-Rust PROS- 1. Just put it in and it works. It dissolves the rust and ONLY the rust. It wot harm the metal. It's non-toxic and non-corrosive. environmentally friendly. It's reusable. What little smell there is, is not offensive at all. Due to space constrictions, I do a lot of my bike repairs in my apartment, so odor counts.  Ultimately, I think it does a better job in the end.

As for the tank I was working on... it developed a leak in the front corner. It had rusted through at the seam and only started to leak in the final stages of the process. Closer inspection of the outside showed that a chip or two had turned into a rusty spot right on the seam. When the inside met the outside in the middle, it was all over. It's a shame too because the outside actually looks pretty good.

Anyway... Can I weld that? JB Weld and seal it? Or should I chalk it up to experience and just get another tank?

Evapo-Rust CONS- The only con is that it's costly. Because of this I couldn't fill the tank to the top and had to keep rotating and shaking it.

Hi,
 have you ever tried molasses?
Works wonders, smells like beer,  gets in all nooks and crannies, does not arm paint or  chrome and is ok for the environement ... But it shure is nasty on rust,
For 20$ worth of molasses and a kid's pool you could dip a hole bike and get it rid of years of rust...
I use 5 water to 1 molasses and it really works great.
The only down side is how long it takes.
From 2 to 4 weeks depends of how bad the parts are.
À+
Crom.


Cromoly.

[Terry in Australia]

Once you've rinsed the tank thoroughly, dry it out as best you're able (a litle methylated spirits tipped in and swished around will help) then once its dry, a small amount of a thin oil (two stroke oil, ATF etc) tipped in and swished around will prevent it from further rusting, and won't hurt your engine. Cheers, Terry.

When I fixed my oil tank I put water in to make sure it didn't leak, then put it in the oven at 250 for awhile to evaporate the water.

Yeah mate, that's a good idea if you can fit it in your oven, otherwise a heat gun works wonders too. Cheers, Terry.

[Retro Rocket]

Once you've rinsed the tank thoroughly, dry it out as best you're able (a litle methylated spirits tipped in and swished around will help) then once its dry, a small amount of a thin oil (two stroke oil, ATF etc) tipped in and swished around will prevent it from further rusting, and won't hurt your engine. Cheers, Terry.

When I fixed my oil tank I put water in to make sure it didn't leak, then put it in the oven at 250 for awhile to evaporate the water.

Yeah mate, that's a good idea if you can fit it in your oven, otherwise a heat gun works wonders too. Cheers, Terry.

I wrap a rag around an airhose and blow air into the tank while submerging it in the sink, no need to dry it out....    And before anyone says "you could burst a seam doing that", the rag lets air seep past while adding enough pressure to find any leaks....

[Terry in Australia]

two seperate issues Mick, I was talking about drying it out, but anyway, your test method is fine, I made a plug for the cap hole so I could pump in say, 10 psi (it has a gauge attached) then I can just submerge it and see where the bubbles come from. Cheers, Terry.