Any hints on fixing a petrol tank?

[liferocks]

Gidday all.
I've got a petrol tank thats been sitting outside (on the bike) for a few years and its pretty rusty. I've read up about it and about how to clean out the rust on the inside and how to solder cracks etc. (It hasn't had petrol in it so its pretty safe by now)
But my problem is that in one patch it has rusted right through, making a hole big enough to fit 3 or 4 fingers into, so i was wondering if this can be fixed by soldering too, or if i should block the hole with something and then solder it in place.
Any suggestions would be appreciated.
Nate

[Blakamin]

Whats it off? might be safer to throw it away and find a second hand one!

[laRIKin]

Yes you could solder a patch on.
I'm guessing that the hole is on the under side.
So the patch will not be seen.

I always fill the tank with water up to the point that I'm working on.(5-10mm)
This minimises the risk of an explosion.
It does mean that the last bit of soldering can be abit of a problem.
As the gases in the tank expand it will blow bubbles in the solder, in the last
bit you do.
So just let it cool abit and try again.
Petrol fumes are a funny thing, they do hang around for along time.
And nothing brings them back faster than a bit of heat.
So be care full.

Some guys I know were cutting up the petrol tanks at Lyttelton harbour.
They had bee open to the air and empty for a long time.
Up until the last cuts, the gas axes were still getting blowing out of their
hands. If they were cutting though any metal that had a over lap.
So treat the tank as a bomb, and you should be OK.
I would then get the tank lined with a plastic tank liner.
This will stop the rust and fill any hole you may have missed.
Also remember that, just because the tank does not leak with water.
Does not mean that it will not leak with petrol.
The molecules are smaller.

But as Blakamin said, it maybe time for a new second hand one.

Have fun, as it great to repair stuff and save money.

[Motu]

When soldering the metal has to be perfectly clean,that's a tough job on a rusty tank.We used to do that on car tanks,use a huge iron heated by a torch.But you are better off welding a patch on - I weld on the thicker metal and then maybe go over it with brazing rod,to fill in the gaps and do the bits that are too thin to weld.When finished use Por15 tankliner (get it from a paint supplier,not a bike shop)Fill the tank with exhaust fumes from a car tail pipe,keep the hose in and car running if you get scared,but I've found just a water flush then fill with exhaust fumes does the trick.

[liferocks]

Thanks guys, I'll have a go at cleaning it up real good then. Then see if its thick enough to weld and if not just solder it.
I was thinking that i'd put a liner in it anyway.
Its of an '86 gsxr400 (the model with the square headlight) and i've rung around and placed a few adds but can't find one anywhere.
Oh well, we'll see how it goes.

[vifferman]

I was thinking that i'd put a liner in it anyway. If you get one of the tank fixing kits, it has three bottles: the first is just rust remover/neutraliser (basically orthophosphoric acid - same thing that gives coke its tang:rolleyes: ), then you rinse that out with lotsa water; the second is acetone, which gets rid of the water then evaporates, and the third is the tank liner, which is basically a thick paint / plastic that uses acetone as a solvent. You can buy the liner on its own, and I reckon it's worth doing that and getting an extra bottle, as it's hard to get a decent thick coating all over with just one bottle. It's fairly viscous and hard to spread everywhere. Note that if you have any rust remaining, it WILL rust under the liner. And soldering will help to ensure you get a nice catalytic reactiongoing, and speed up the rusting process.:doh:
I had a VF500 with pinholes on the side opposite the fuel tap, where water would tend to sit and not get flushed out. I was very careful about it, but never quite got rid of one hole, despite several soldering attempts. I was trying to minimise the amount of destruction so the tank wouldn't need repainting.
If I had to do it again, I'd bite the bullet, and have it brazed, use two lots of tank prep, and repaint the tank. Do it once, do it right.

[Mongoose]

Thanks guys, I'll have a go at cleaning it up real good then. Then see if its thick enough to weld and if not just solder it.
I was thinking that i'd put a liner in it anyway.
Its of an '86 gsxr400 (the model with the square headlight) and i've rung around and placed a few adds but can't find one anywhere.
Oh well, we'll see how it goes.

Personally I would shy well away from a petrol tank with any hot flamey thing. As someone said, petrol gasses are a funny thing and lurk inside petrol tanks for ages and ages and ages.
Hot iron for soldering maybe, but no, nope, no hot flamey sparky thing for this kid, to much risk of BOOM! and up she went.

[kerryg]

Personally I would shy well away from a petrol tank with any hot flamey thing. As someone said, petrol gasses are a funny thing and lurk inside petrol tanks for ages and ages and ages.
Hot iron for soldering maybe, but no, nope, no hot flamey sparky thing for this kid, to much risk of BOOM! and up she went.

I had a very good result patching a petrol tank with the bog stuff that comes in a stick (you knead it to set of the curing reaction reaction). I got it at Repco and it literally sets like steel, and it sticks like s**t to a blanket. There are a few varieties of it so look for the one that says it can be used for petrol tank repairs. I can tell you from experience that ordinary bog lets petrol straight through.....:Oops:

[vifferman]

I had a very good result patching a petrol tank with the bog stuff that comes in a stick (you knead it to set of the curing reaction reaction). I got it at Repco and it literally sets like steel, and it sticks like s**t to a blanket. Yeah, it's a very solid epoxy. Jesse James used it one time on "Monster Garage" when some numbnuts didn't test a tank he'd welded up, and it pissed diesel everywhere when it was filled up.

[liferocks]

Cheers again guys.
I hadn't thought of that bog stuff, I'll have a look for some of that.
If it'll still rust under the liner how do you manage to get all the rust out, is that acid stuff that comes with the liner good enough?

[Motu]

Yeah,it's good stuff,will kill it dead,then you put in the liner.Actualy Jenolite is just as good.Heat the tank with a heat gun or hair dryer,this will get the last of the water out,then put the liner in when it's still warm.I got a litre tin I Por15 about 5 years ago,have used it heaps and have 1/3 left,much cheaper than buying the kit.

My XLV750 tank is the worst I have ever attempted to repair,they are not exactly falling out of trees.I had it acid dipped and it came back looking like a cheese grater,smashed in both sides,had been cut open and welded up in a couple of places to panel beat it into shape,big holes and pin holes everywhere.I patched the big stuff and tried to seal all the small holes with weld or brass - but evey time I put a torch near it rust would ping off the inside.Finally I got it to the point where it would just seep water out of half a dozen holes,then I put the liner in - Kream first,but it's very thick and didn't spread well,so did a second coat with Por 15.It's been in over 4 years with no leaks.Took a couple of goes to seal my TLR200 tank too.

[liferocks]

Awesome. Thanks Motu
Where did you get it acid dipped?
Or what acid did they use?

[vifferman]

Finally I got it to the point where it would just seep water out of half a dozen holes,then I put the liner in - Kream first,but it's very thick and didn't spread well,so did a second coat with Por 15.Yeah, the Kreem is what I used, and it's hard to spread around. I reckon you could thin it with acetone, but if the Por15 works well, then why bother with the Kreem?

[Motu]

Awesome. Thanks Motu
Where did you get it acid dipped?
Or what acid did they use?

A furniture stripper could do it,but they don't like car and bike parts because of the oil and grease - but if you took it along and showed how clean it was they might let it in the tank.I think our local guy ''**** the Stripper'' has a problem with me personaly,he said no even before I opened my mouth.But close by is a crowd that does total immersion of complete car bodies,so it was no problem to drop it in a corner.

I'm a bit suspicious of this dipping,I have never seen a tank so rusty,it looked like it had spent all it's life out in a paddock,but when I took it off I didn't think it looked too bad,it's almost like they took it out of the tank and let it sit for a few weeks still soaked in acid (or alkali,whatever they use),but it was only a one or two day turnaround.I'd have to do a known good tank as a control.But if they dip complete vintage car bodies they'd soon have some angry customers if they rusted out after dipping.

[laRIKin]

A good trick for cleaning out your tank, is to put some nuts or chip (stones).
In your tank and shake the bejesahs out of it, but not so hard that you dent the tank.

And count the stones or nuts to make sure you get them all out.
And then flush the tank out well.

[kerryg]

A good trick for cleaning out your tank, is to put some nuts or chip (stones).
In your tank and shake the bejesahs out of it, but not so hard that you dent the tank.

And count the stones or nuts to make sure you get them all out.
And then flush the tank out well.


Another way is to use a bit of chain. Then you don't have to worry about bits being left in the tank.

I need to clean out a slightly rusty tank (on the inside). It's far from being so bad that it might leak (it's just specks of rust). I don't reckon it needs the full Kreem or POR15 treatment, just needs to have the pre-treatment stage that removes the rust. Anyone tried one of the off-the-shelf rust removers places like Repco sell? Or anyone tried to make up a phosphoric or hydrochloric brew themselves??? Kind of reluctant to part with $70 or $80 if I can avoid it, and I don't want to put a coating on the tank unless it's necessary (which it's not) because of stories you hear about the coating coming off over time

[vifferman]

Another way is to use a bit of chain. Then you don't have to worry about bits being left in the tank.The problem with that is it wouldn't get into all the little corners. Mind you, neither would gravel (what I used) or nuts.


I need to clean out a slightly rusty tank (on the inside). It's far from being so bad that it might leak (it's just specks of rust). I don't reckon it needs the full Kreem or POR15 treatment, just needs to have the pre-treatment stage that removes the rust. Anyone tried one of the off-the-shelf rust removers places like Repco sell? Or anyone tried to make up a phosphoric or hydrochloric brew themselves??? Just use any 'off-the-shelf' rust remover/neutraliser. While you could use some other acid, it'd only eat the rust, and that's all it would do. The orthophosphoric acid is used, as it turns the ferrous oxide (rust) into a more stable phosphate salt, which doesn't continue to oxidise. Also, orthophosphoric acid isn't as nasty to handle as some other acids, and works well when diluted. Just check the label on the bottle to see what it says before you buy it.

[kerryg]

The problem with that is it wouldn't get into all the little corners. Mind you, neither would gravel (what I used) or nuts.

Just use any 'off-the-shelf' rust remover/neutraliser. While you could use some other acid, it'd only eat the rust, and that's all it would do. The orthophosphoric acid is used, as it turns the ferrous oxide (rust) into a more stable phosphate salt, which doesn't continue to oxidise. Also, orthophosphoric acid isn't as nasty to handle as some other acids, and works well when diluted. Just check the label on the bottle to see what it says before you buy it.


Ta for that. I think I'll try that.

[scumdog]

I have successfully used a 50-50 mix of mollasses and water and left the rusty item in it for a few days and it clears all rust that is not too thick.

You could fill the tank with that mix for a few days, it'll get surface rust pretty quick after you flush out the mollasses mix so you will have to flush it out with a commercial phosphoric acid type rust-kill.

Small holes I have tackeled by drilling the hole to suit a pop-rivet and using a smear of f'glass resin on the rivet before putting it in place, mind you it might not look too flash if there are a dozen or so random holes where you can see them!! :o

[kerryg]

I have successfully used a 50-50 mix of mollasses and water and left the rusty item in it for a few days and it clears all rust that is not too thick.

You could fill the tank with that mix for a few days, it'll get surface rust pretty quick after you flush out the mollasses mix so you will have to flush it out with a commercial phosphoric acid type rust-kill.

Small holes I have tackeled by drilling the hole to suit a pop-rivet and using a smear of f'glass resin on the rivet before putting it in place, mind you it might not look too flash if there are a dozen or so random holes where you can see them!! :o


S'pose you could throw in some yeast and then you'd not only get your tank clean but you'd get rum as well.....what's that cocktail???....."a rusty nail" :killingme ...OK I'll go away and kill myself now :thud:

[scumdog]

S'pose you could throw in some yeast and then you'd not only get your tank clean but you'd get rum as well.....what's that cocktail???....."a rusty nail" :killingme ...OK I'll go away and kill myself now :thud:

Yeah, know what you mean, sometimes on a hot day my gargre smells like somebody has been on the rum, smell comes from my rust-cleaning brew

'I wouldn't want to join any organisation that would have ME for a member" - also Groucho Marx.

Also: "either this man is dead or my watch has stopped" - said while trying to take a pulse on someone.

[muppitt]

Before welding any gas tank Degas it first. that is to run exhust gas though for tewenty minites .remove the fuel tap for an out let and run a hose from you car tail pipe into the gas tank filler . the carbon dioxide neutralises any petrol fumes .so we wont have to hose you off our roofs

[kerryg]

The problem with that is it wouldn't get into all the little corners. Mind you, neither would gravel (what I used) or nuts.

Just use any 'off-the-shelf' rust remover/neutraliser. While you could use some other acid, it'd only eat the rust, and that's all it would do. The orthophosphoric acid is used, as it turns the ferrous oxide (rust) into a more stable phosphate salt, which doesn't continue to oxidise. Also, orthophosphoric acid isn't as nasty to handle as some other acids, and works well when diluted. Just check the label on the bottle to see what it says before you buy it.


Thought I'd give some feedback on this. I tried the Repco rust remover (can't remember the brand but I think it was made by Newtech...it was one of that stable of body repair products that Repco stocks ) and it wasn't much use. Didn't seem to do anything actually.So I bought the POR 15 equivalent called Metal Ready and it worked a treat. My tank is now good as new or very nearly. Both products phosphoric acid based, so beats me why the difference. So I can recommend Metal Ready for de-rusting the inside of petrol tanks. Best thing is that the instructions for Metal Ready said the product can be re-used repeatedly (just should filter out any debris) so I've recovered and will re-use 800 of the 1000 mils I bought. At $30 odd for a litre it's not cheap which is the one thing against it

[vifferman]

Thought I'd give some feedback on this. I tried the Repco rust remover (can't remember the brand but I think it was made by Newtech...it was one of that stable of body repair products that Repco stocks ) and it wasn't much use. Didn't seem to do anything actually.So I bought the POR 15 equivalent called Metal Ready and it worked a treat. Fancy that. ONe would expect something sold as a rust neutraliser would actually be strong enough to do a decent job! Otherwise, you may as well use coke....
Were there any indications on the bottles/tins as to the acid strength? I'd imagine the Repco stuff was diluted a tad, to make it more saferer / increase the profit margin.

[kerryg]

Fancy that. ONe would expect something sold as a rust neutraliser would actually be strong enough to do a decent job! Otherwise, you may as well use coke....
Were there any indications on the bottles/tins as to the acid strength? I'd imagine the Repco stuff was diluted a tad, to make it more saferer / increase the profit margin.


I don't understand it either. The conditions were the same pretty much in both cases (similar sort of temperature, same quantity, same method, similar length of time) so I guess it could be down to concentration or perhaps other stuff mixed in with (I'm no chemist as you can tell). There wasn't anything on either package to indicate strength so far as I can remember. But the results were remarkably different. Unless the first application removed some shite and shanky (residual petrol or varnish?) and so the second application was able to work on a better surface or something like that. I dunno.

Phosphoric acid is as cheap as chips of course. Any industrial cleaning chemicals outfit is using it by the tanker load. Hard to figure why a litre of dilute phosphoric should cost $30...

Anyone tried acetic acid (vinegar) for de-rusting? Just a random thought. I know it cleans metal surfaces real well...does it deal to rust? Now vinegar is only, what, $2 0r $3 a litre.....???