(Victory Runner)
11/14/16 04:30 PM
GVR4 gas tank rust. - solved.

Hi All,

Been a while since posting or properly wrenching on cars, but here is one issue I recently tackled, so I thought I'd share here as it should prove useful to all.
It looks like the .org is a little quiet so please enjoy my journey here

Situation: Need to paint the front of the house so the Galant has to move. I'd not started it for almost a year. When I returned to the UK I drained the fuel, and It was not good, but fresh fuel, a good battery and jumpleads got it going. This time I was not lucky.. So I decided to pull the sender and see what I had to work with:

After seeing this sight I felt sick... These things are rare here and it felt like a death sentence for the car... already there in my wife's eyes

So I got my thinking cap on and wanted to see where I could take it. Dousing with WD40 it looked like this:

Really not good, so my options were limited. M5 Bolts are fragile, but thinking outside the box gave me an idea.

Heat? No(its a gas tank)
Cutting? No(too close to the fuel line)
Expensive chemicals? No. need to do this without much outlay.
Penetrating oil? I wanted something with ultra low surface tension so came up with this solution:

Using brake cleaner and WD40 althernately to wiggle the bolts back and forth. With the brake cleaner it penetrated the thread, and wiggling allowed the crud to be 'washed' out. I was amazed and jubilant when all the bolts were removed. This was short lived as when I lifted the sender out it was clear the car was trying to tell me something:

Crusty is not a word really appropriate here. The sender had tide marks on it!

Still everything was in one piece, no holes, not bashed up, just very very crusty.
I dropped the tank as something had to be done now..

and inside here is what awaits!

So while I waited for ideas and opportunity here I tore into the sender. Now this car is an early '88 and the sender is the slide on pipe type. I ordered a sacrificial unit from a NA 3kgt, so I had parts to cannibalise/cut up if needed. Here is the galant sender spread out for all to see:

Now I bet most are reading here and going holy smoke what the heck are you going to do with that...
I cleaned the sender parts up, zinc coated the frame and blacked it.

Here it is back together:

Not perfect, but a good long way forward from where it was. So onto the tank next, while I was doing the sender a company had the tank to check for holes and fill them in, it was repaired and cleaned a bit, but as soon as I got it home the thing was rusty again inside. They used HCL and no passivation, so it flash rusted good by the following day. Not good.

I searched and thought I'll try some home chemistry here.. I saw a couple of techniques for doing motorcycle gas tanks, so I put them together.
Basic principle is electrolysis, use electric current to reverse the rusting process:

Ensure you have BIG pails here.

1/You need a sacrificial anode (IRON) NOT STAINLESS!. I used some threaded mild steel bar with the zinc removed. (NOT STAINLESS!!! WILL POISON YOU AND THE ENVIRONMENT).
2/ Insulation. The tank contains many baffles and internal protrusions. You need to isolate these so no shorting occurs. I saved nylon netting we used to receive round tools in at work. I linked them together to form a sock and cable tied them so I could load and unload my insulation. Double bonus as this was full of holes to allow good electrolyte circulation.
3/ Sturdy support at elevation. You will be moving large amounts of fluid, and will want to see any leaks (quickly). So best to have the tank at a working height, support needs to be steady and strong, full to the brim it takes about 75litres of water.
Keep in mind you need the sender end high for the bath, and low for draining completely.
4/ Electrolyte: You will only need about 1kg of washing soda. I used about 1.25Kg and mixed it into very hot water about 50% into 40 litres the poured it in the sender hole. then same again for the other 40 litres.
5/ Block all external holes, hoses etc... simples really.
6/ Phosphoric acid (drain cleaner/milkstone remover) Need lots and a good concentration. I used 6 litres at 30% strength (you need this after the electrolyte).
7/ Drying apparatus. (I used a vet/dry shop vac that can also blow, and a heat gun).

#1 Electrolysis:
Once set up and questioning my sanity I used a pair of fat jumper cables and 70ah car battery. I hooked my charger up to the battery, so it would act as a big capacitor, and let it go. (MAKE SURE THE POSITIVE IS ON THE SACRIFICIAL ANODE).

I let it run for about 4-5 hours, after each hour I took the anode out and cleaned the muck off it then put it back. You can see here the nice film of sludge forming on the top of the electrolyte.
Cleaning the anode:

You can see the netting sheath here too.

After time was run I drained the tank quickly while wiping the inside,

#2 Phoshphate pickling.
I immediately flushed with hot water and refilled with phosphoric acid and very hot water to make the balance up. I rigged a heat gun to warm the tank as it was sitting.

Here it is with the phosphoric solution inside. The difference was quite exciting at this point:

#3 Draining.+ Drying
Here you need to be quick and get rid of that moisture quickly. I had a 2000W blow gun and a shop wetvac ready to go.

Draining, here's why you need the massive pails...

Fluid going down... looks amazing doesn't it!

When it was low enough that I could lift it outside i took the wet vac and blow gun to town, roasty toasty and dry:

I didn't take many pics here as I was trying to get wrapped up quickly before it flashed too badly.
I then mixed up 5 litres of gas with 1 litre of white spirit and 250ml of quality 2 stroke oil (silkolene comp 2). and washed and sloshed it round inside.

Now it's not 100% but soo much better than the stomach churning mess when I took it apart.

I ducktaped the holes up and put it to one side after giving it a very good sloshing.

I took some time on the underside of the car to make it look spangly above the tank..

Yes I know the rest looks mighty crusty...

Scratched down with 3m pads on a drill, and wiped with brake cleaner. then zinc primered and undersealed.

Tank all build up and ready to go back on:

The new inspection hatch view:

With all the shiny bits and the helping that the eldest was doing he was now asking questions of the car, why are you working on this junk pile dad? Up to now it has been hidden under a cover out front, well it's on it second cover and that's quite mucky too. so when I took it off to reveal the car in it's waxed glory his jaw dropped.

We filled it with gas from gas cans and put tank conditioner in, then it cranked and cranked an fired!
He said what can I do to help? Here his is pumping up the tyres:

Then, hopefully oneday...

Now that's a smile

Still it's a long way to go, but it moves under it's own steam again!



HertzGalant VR4.org Administrator
(OneTitle to rule them all.)
12/02/16 04:30 PM
Re: GVR4 gas tank rust. - solved.

This is amazing!

(fighting them with a large needle)
12/03/16 08:24 AM
Re: GVR4 gas tank rust. - solved.

Good job!

(Space Blanket from NASA plumbed into the attic)
12/22/16 04:58 AM
Re: GVR4 gas tank rust. - solved.

Something Ive been using lately on surface rusted /plated items before I weld is muratic acid. You dip it in let it cook then just rinse, dry then weld. Do it outside with gloves glasses etc. shit will screw up your day if it gets in your eyes. I have like 10 buckets full of items I need to clean up before I weld and I may use your tech instead of acid. 7 bucks a gallon is cheap enough but I can do about 20 to 25 items with a gallon and I have over 500 to do.

(Senior Member)
12/29/16 04:13 PM
Re: GVR4 gas tank rust. - solved.

I swear every time you post up something I end up learning lol. Very informative.

(fighting them with a large needle)
01/02/17 08:01 PM
Re: GVR4 gas tank rust. - solved.

Quoting curtis:

Something Ive been using lately on surface rusted /plated items before I weld is muratic acid. You dip it in let it cook then just rinse, dry then weld. Do it outside with gloves glasses etc. shit will screw up your day if it gets in your eyes. I have like 10 buckets full of items I need to clean up before I weld and I may use your tech instead of acid. 7 bucks a gallon is cheap enough but I can do about 20 to 25 items with a gallon and I have over 500 to do.

I've been using the same thing for years now on any rusty parts and agree that it works great. It will completely strip the rust off of metal.
My current VR4 came with an ETS FMIC kit that had been sitting for years in storage so the mild steel piping was rusty inside. Swished some HCl toilet bowl cleaner around in the pipes and they were shining like new before coating them with POR15. That stuff is a huge time saver and super cheap!

(Eager Beaver)
01/04/17 11:33 AM
Re: GVR4 gas tank rust. - solved.

Handy reference for household products and their percentages (US system):

Click for hydrocloric acid contents for household products.

(Victory Runner)
01/06/17 06:30 PM
Re: GVR4 gas tank rust. - solved.

Hi Curtis,

Muratic or HCL is what was used first, but it's way way too agressive and flash rusted like a banshee in a few seconds. The Phosphoric uses different chemistry to passivate the free iron. A very slight phosphating.

I did that after using the electrolysis to reverse the rusting.



(Junior Member)
05/31/17 10:15 AM
Re: GVR4 gas tank rust. - solved.

Very well done. Nice job.

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