Gas Tank Rust

[Crossrodes]

Actually it may have been me that brought up the coke idea some time back.  A friend of mine used it to free up his through hull fittings on his boat...left it in for 24 hours and it worked like a charm.  But as Bob says, it may not dissolve the painted liner and that's what I have to do first.  The coke will work on the rust though...maybe a second stage idea if I don't go with the POR-15 product to get rid of the rust.

At 12:45 pm today I put about 22 litres of 5% acetic acid white vinegar into the tank.  I filled it to the brim.  We'll see how long it takes to do the job.

I did get the bungs at a wine supply store Bob but they have a hole in the middle to allow it to gas off.  The small one I bought for the petcock hole was too big and I couldn't shave it down very easily so I found a cylindrical shaped tool in my tool box that was just a tad smaller than the inside diameter of the outlet.  I cut some old inner tubing to fit over the tool and pressed it into the outlet.  It's holding now but I'll see if the vinegar does a number on the inner tube over time.  I may have to replace it.   Maybe I should have put some saran wrap over the inner tube  

[Bob_Roller]

I had the molasses solution in my fuel tank for around 3 weeks and it didn't do any harm to the rubber stoppers .

I got smaller rubber stoppers to plug the hole in the large rubber stopper that goes in where the fuel cap sits at a home improvement store (Lowes), I believe they were in the packaged hardware section that is usually in steel cabinets with drawers .

[Crossrodes]

Bob what would be your guess as to how long I will have to wait with the vinegar in the tank?  Also would you recommend that I occasionally turn the tank upside down to ensure the top of the tank is getting treatment?  It is filled right to the top the two vents in the the fill neck right now.

[Bob_Roller]

I'd guess leave it alone for 10 days, then see what the condition of the interior is  .

You're going to need to turn the tank upside down, as there is an area at the top of the tank that is not in contact with the liquid .

[DanielMc]

I've used the POR 15 and whilst the results were acceptable it was a real hassle to do.

I've heard great things about removing rust using a solution of sodium carbonate (washing soda) and electrolysis: remove fuel tap and bung the hole, fill the tank with the soda solution then hang an old chisel in the tank making sure it can't touch the tank itself. Hook this sacrificial anode up to the positive of a 12v battery and connect the body of the tank up to the negative terminal. One refinement is to put the battery on charge whilst this is going on. Leave in situ for around three days removing scum from the filler hole and making sure the electrolyte level stays good.

This leaves the tank clean but uncoated. I plan to use this system when I'm next faced with cleaning out an old tank, and I'll probably leave the inside bare and just inspect annually. New paint etc. is as likely to create as many problems as it solves due to the amount of ethyl alcohol in fuel, and resin lining (like the POR 15) only works if perfectly applied.

[Bob_Roller]

The POR 15 and Kreem, the only two products that I've seen available locally, really stress on getting the tank free of crud inside the tank, I know the products don't adhere very well to the OEM liner .

POR stands for 'paint over rust', I've been told by car restorers, that POR 15 is more tolerate of rust in the tank than Kreem .

The prep work for relining the tank is a pain which ever method you choose .

Like any painting project, 80 % of the work is in the preparation .

I'd like to hear how the electrolytic method works out on your fuel tank .

[Crossrodes]

Daniel that electrolytic systems sound interesting.  I think I'll consider it when I do the next step to get rid of the rust.  Do you think a marine sacrificial anode would work as well as an old chisel (I don't want to sacrifice a chisel).

[DanielMc]

Daniel that electrolytic systems sound interesting.  I think I'll consider it when I do the next step to get rid of the rust.  Do you think a marine sacrificial anode would work as well as an old chisel (I don't want to sacrifice a chisel).

That's a good question - my understanding is that the sacrificial anode needs to be mild steel in order to react with the iron oxide (rust) in the tank, so any piece of steel rod or bar should suffice. Here's a website showing the process using a coat hanger: http://www.ehow.co.uk/how_6827738_clean-gas-tank-tap-electrolysis.html

My experience of marine anodes is that they are usually made of something like zinc in order to protect expensive aluminium alloy boat components and so probably wouldn't work, however as I've never attempted this technique what do I know!

Like others here I'd be keen to hear how this technique works in practice.

[Bob_Roller]

I don't know if the composition of the anode is critical or not, you could try just a plain old piece of steel or iron as an anode .

Again just thinking here, but you may need a large surface area for the anode to work, or you may need to change a smaller one if it gets covered completely with transferred material from inside the tank .

[montmil]

From my experiences, a piece of concrete rebar, used as an anode, works well.

Monte

[Crossrodes]

Rebar sounds good...got lots of that...and it's rusty.

[balibeemer]

The best solution for rust inside the tank is to use a 10% solution of phosphoric acid. I cleaned out the tank with the following procedure:
1. Empty the fuel
2. Remove tank from bike and remove petcock(s). Plug petcock holes( I use trimmed wine corks)
3. Wash with hot water and detergent (1/2 full and rock the tank back and forth)
4.  Add 20 litres of cold water and then 2 litres of Phosphoric acid  ( water first, THEN the acid.
5. Allow to stand 24 hrs
6. Empty the tank.
7. Flush with a baking powder solution of 4 tbsp to 10 litres.
8. Spray the inside with WD 40 (dewatering)
9. Flush with thinners.
10 Seal tank with a proprietary sealant, or denture fixative (just joking!)

Ive used this on 2 tanks with very good results!

[Crossrodes]

Well the tank has been "almost" full of vinegar for almost 2 days now.  I just noticed that the liner is starting to detach from the tank.  I scraped the inside of the neck, where there is vinegar, with my finger nail and  most of the liner in the neck came off.  So it's working.

[Bob_Roller]

Good to hear it's working !

What's the temperature of the tank, any id, I'm going to guess it's on the cool/cold side ?

[Crossrodes]

The tank is sitting in my basement and it's a little cool down there.  I'm guessing it's about 67-68F.  Would it work faster if it was warmer do you think?