Caustic soda - petrol tank. Page 1 / 2

201, Sep 8, 8:58pm
Has anyone used caustic soda to clean rust etc out of a steel motorcycle petrol tank? I'm wanting to know how much to put in tank & how long to leave it in.I have used Evaporust to no avail. Not interested in expensive wash/sealants etc. It's caustic soda advice I'm looking for thanks.

intrade, Sep 8, 9:17pm
just get white vinnigar to remove rust its cheaper i would say

201, Sep 8, 9:24pm
Thanks "Intrade" how much white vinegar? fill it up & leave for day or just few hours?

intrade, Sep 8, 9:34pm
fill it up and let it site for 2 to 3 days then wash it out and save the vinnigar . once vinigar is no good youl know it. it sortof bubbles when it does its job

intrade, Sep 8, 9:42pm
then i would flush it out with water . and if its clean chuck some gullforce 10 fuel in there as it containse ethanol who binds water and flush it abouts and drain it again and it shoud be fine . you may end up with leakes holes however where the rust has gone thru the tank.
this video is what happens its no fake i done it turns steel black ish and you got to clean or it rusts quickly again from water oxidation .
be awear ethanol fuel its the only place and time id ever use that i dont want ethanol in any of my fueltanks . but for this its seems perfect. light a fire or give it to a farmer to light some outdoor fire carfully as petrol lighting is also dangerous. " as in how to dispose the gullforce 10 used to remove vinnigar water based contermination from tank"

gsimpson, Sep 8, 9:49pm
Molasses and water is effective at removing rust. Takes 2-3 weeks to work but will not harm the steel and just be rinsed out.

intrade, Sep 8, 9:51pm
*6 molasses are real expensive not to mention sticky and not easy to remove like cheap white vinnigar. but yea that would work its just less then ideal in this case.

apollo11, Sep 8, 9:57pm
Caustic soda is lethal stuff, great for getting grease spots out of concrete. Stir it very slowly into warm water- add it too fast and it will explode (say bye to your eye brows). Eats aluminium very quickly too so be careful.

marte, Sep 8, 10:06pm
You can buy Phosphoric acid from a Hydroponic shop & 200mls of that poured in and washed around to coat it, then a swish every 5 minutes for a hour & pour it out.
Some sort of abrasive would help, crushed glass maybe? The little squares from broken safety glass? Or such, added with the acid.
Then wash it out several times with water, then wash again with some baking soda in it, wash twice again with water & I would use Meths to clean the water out.

Phosphoric acid is great for cleaning the inside of Stainless steel pots too. A tiny bit of heat helps.
It's a strong acid, so gloves & safety glasses are needed.

But put a drop of it in a teaspoon of water and touch a finger tip into it & taste it & you will know exactly what food product it's used in.

It would do a good job ( diluted of course! ) Of cleaning rust from toilet bowls, maybe concrete too.

4.11, Sep 9, 7:17am
I went through all of this and nothing actually works any good, ended up cutting the tank in half, bead blasting the rust out, tig welding back together, mind you this was only a lttle suzuki LT50 fuel tank, I was to cheap to get a new one, it was particularly bad at the seams so no amount of rust killer or acid would have fixed this without cutting the tank open

alowishes, Sep 9, 7:32am
Molasses + water 50-50.
Cheap-as from stock and station agents.

Fill tank for 4-5 days,
Pour out.
Spray inside with CRC.

Molasses non toxic.

bigfatmat1, Sep 9, 12:47pm
Wouldn't any sort of corrosive solution be worse for treating rust. It would just rust out again quicker

bigfatmat1, Sep 9, 12:51pm
Phosphoric acid is what you would use as it stops further rust

apollo11, Sep 9, 12:53pm
I wonder if it's possible to zinc electroplate the inside of your tank to protect it?

desmodave, Sep 9, 4:23pm
Or you could keep the tank full of fuel to leave less room for air . Por 15 do a tank re sealer kit and there are others .

intrade, Sep 9, 4:29pm
i think you can only electroplate clean metal not rust.

desmodave, Sep 9, 4:32pm
If you got the idea , theres probably a youtube cip all about it . Myself i would be thinking can you trust this youtube star or internet recipes full stop .Just make it up as ya go if you don't want to spend any coin , keep an eye on it for sure . Gunna be hard to show us a pic of the results no doubt .

apollo11, Sep 9, 5:47pm
Once you have treated a tank for rust I mean. Modern tanks look like they are already made from zintec or similar, and it does give limited protection from rust initially.

201, Sep 9, 6:29pm
Many thanks guys, I'm going to give the white vinegar a go, followed up by water with baking soda to stop any vinegar deposits left causing trouble.
Need to dry tank after couple of flushes with hair dryer seemingly.
thanks again for advice. P.S. its 1970 BSA tank so reasonably decent steel.
And yes I know "new" ones can be bought out of India but they are not 100% accurate to original design.

wheeler1, Sep 9, 8:43pm
The best way to dry a fuel tank once its been washed with water is to remove the fuel gauge and use a vacuum cleaner on the blow setting it warms the air coming out .Poke in in the filler hole .Dont use the suck side for obvious reasons

desmodave, Sep 10, 3:10am
A 1970 BSA what , A65 / Rocket 3 / Lightning ? . So you get your tank clean then what . Would of thought seeing as they don't make them how you would like it , would be more reason to spend $70 or $100 odd on a clean & seller kit . 1 particular friend that bought a new evo Harley every couple of years would still chem clean seal kit ( think that was the name ) the near new tank .Apparently 1 leaked once so he would do that to every new bike . Then it was off with the heads to fit Black Diamond valves .Good luck with it . Should be easy for your tank as no efi so no fuel pumps and filters to remove 1st .

desmodave, Sep 10, 3:16am
You can just place it over a car exhaust if it happens to be at the right height , let it idel while ya go have a cuppa .

201, Sep 10, 8:30am
Thanks Desmodave, its a 441cc Shooting Star. Did own a Rocket 3 some 42yrs ago !. Beeza looks good beside my Ducati. Spent $85 on Evaporust
so getting frugal now. Got 16ltrs vinegar last night for about $38.

alowishes, Sep 10, 8:55am
Best done on a warm dry day - just look at the condensation that comes out of exhaust when it’s a cold wet day.

Humid air into engine means humid air out, the water in the air doesn’t burn.

desmodave, Sep 10, 11:09am
Nice , got to save coin for tyres and fuel then . Those triples do put out a nice sound but anything with 2 wheels and a motor will put a smile on ya face .

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