muriatic acid a good idea?

i'm wondering if using muriatic acid to de-rust a gas tank has any negative effects? i know all the info about not letting the acid touch the aluminum petcock or any rubber or plastic...but is there anything to be wary of as far as the actual tank is concerned? i've used the stuff for cleaning out one tank and it seemed to be fast and effective, and have had no ill consequences so far...just not sure if i should make a habit of it. any suggestions would be nice. thanks, y'all.

Re: muriatic acid a good idea?

Go for it... it's the best!

Nice Magnum btw.. just like mine!... What carb/intake/jet/air filter are you runnin with the Biturbo?

Re: muriatic acid a good idea?

See Ya Moped Army /

Keep the tank filled with gas/oil premix or the tank will eventually rust worse than before.

Re: muriatic acid a good idea?

Luke, if you use the search function you can find several threads about this, but basically you're supposed to follow the muriatic acid wash with a phosphoric acid wash, it reacts with the newly exposed metal somehow and produces a more rust-resistant layer. Some people have used Coca-Cola (which contains phosphoric, citric, and carbonic acids) instead of the harder to find and more expensive phosphoric acid. If you use Coke, you need to make sure you've rinsed out the sugary residue... you can use denatured alcohol for this (it will also dissolve dried-up gas varnish).

I don't know if this is a good idea or not, but it might be cheaper and easier to use 91% isopropyl alcohol instead of denatured, you can get it at most drug stores. 72% is probably no good, it's 28% water and the leftover water can start re-rusting your tank, but in my experience the 91% evaporates pretty completely. Never tried it in a tank, though.

Re: muriatic acid a good idea?

that stuff works fine just make sure that you keep gas and oil in your tank or it will rust right back up

Re: muriatic acid a good idea?

Muriatic acid is one of my favorite chemicals.I deal with a lot of rusted parts,and muriatic acid is the best,and cheapest,rust remover I know about.I probably use 20-30 gallons of it a year.As long as you know how to use it safely,you are fine.It will not harm the tank in any way.In the few cases where I've had pinhole leaks show up in a tank that I cleaned with muriatic acid,the tank was so far gone that it was junk anyway.If it's a super rare or otherwise irreplaceable tank,the holes can be repaired by welding.I repaired an early '60s Honda tank that had several small leaks along the bottom seam by welding a bead all the way along the inside edge of the seam.If it is a larger hole,I've seen sheet metal plates welded over the hole,and then feathered in with bondo.Just remember,you have to get rid of ALL the gas and gas fumes before welding on a tank.Otherwise,you might as well be welding on a bomb.Anyway,after using muriatic acid to clean the tank,I recommend a thorough rinse with water,followed by a thorough soaking in WD-40,immediately,before the tank dries and surface rust forms.WD-40 displaces water.Seal the filler and petcock openings to keep dirt out until the tank is ready to use.Pour out any excess WD-40,and pour in premix.What little WD-40 is still in the tank won't hurt a thing.Peace.Jerry.

Re: muriatic acid a good idea?

So....will small amounts of rust, not particles but just surface rust screw with my moped starting? I have minimal rust in the tank and lately it has been hard to start. I drained the tank and noticed the fuel was a little orange. But I see no 'flakes'.

Re: muriatic acid a good idea?

Rust is iron oxide, and a conductor of electricity. I've seen bikes with very fine rust in the tank, that repeatedly fouled plugs. The rust was fine enough to be carried in the fuel stream, and onto the spark plug - where it eventually caused a short.

Well, not quite a short, but a less-than-infinite resistance - and that's fouled.

Re: muriatic acid a good idea?

thanks alot for the info, guys. the tank is clean and rust free now, and the qt50 is runnin smooth. cheers!

Re: muriatic acid a good idea?

Rust is not only a conductor for electricity but also a harsh abrasive when it contacts moving parts. It is important to clean the rust from the tank to prevent sdamage to your fuel system and your engine.

Muratic acid is a very powerful acid that you do not want on your skin. Also be very careful of the fumes that come from the acid etching the metal. You do not want to breathe these fumes! Being that it is an acid, you should use a base such as baking soda(mixed with water) to nuetralize the acid after cleaning. Then rinse with water, and last with isoprpyl alchol to remove any moisture.

To do it right you can then seal the tank with POR-15 or another gas tank sealer. POR-15 is about $30 dollars for the kit but it is the best! One kit will do about 20 tanks. The only downfall is that it is a two part epoxy sealer meaning that it is has to be used all at one time or it goes bad. So get together with your buddies and do a bunch at one time to save some money.

Re: muriatic acid a good idea?

I pretty much agree with you on everything except using a tank liner.ANY brand of tank liner will eventually start coming loose,and then you've really got a problem.If you get the rust out,and the tank does not leak,just keep it full of premix,the oil will keep the inside of the tank oily,and it won't rust anymore.Doesn't hurt to use a fuel filter either.Peace.Jerry.

Re: muriatic acid a good idea?

I use Behrs Concrete and Rust etcher, its phosphoric acid, and it works reall well, the last tank i did i let it sit in the tank for about 4 days, then i pressure washed the inside of the tank, looks clean as can be

i have used sealers, but usually find them too be more trouble than they are worth, so i just get them real clean and keep them full of gas and oil

Re: muriatic acid a good idea?


Here is another alternative that you might consider.

For my motorcycle restorations I use a product called Sudco Rustol. It is a bit spendy but no nasty chemicals. It is odorless and non-corrosive to all metals, rubber coatings, or paint. The same batch can be reused 4 to 5 times.

This stuff works great!!!!

See more information on Rustol here:


Re: muriatic acid a good idea?

I've seen it advertised in Walnecks Cycle Trader.It has a good reputation,but if I remember correctly,it's super expensive.Peace.Jerry.

Re: muriatic acid a good idea?


Yes, it is a bit pricey (45.00) but the same batch can be used to clean several tanks.


Re: muriatic acid a good idea?

dont drink muriatic acid. it gives you real heartburn

Re: Epoxy use

Epoxy should have a "shelf life". I agree that once mixed it will harden, but I don't see why it needs to all be mixed at once. As long as the correct ratio of resin to hardener is used the quantity mixed should make no difference

Re: Epoxy use

It comes already pre-mixed in the can right from the maufacturer. It is probably vacuum sealed or something to prevent the activator from causing it harden immediately. This is just what I remember reading on the can. I am sure that there is plenty of info published on the web about POR-15 gas tank sealer.

I have cleaned many tanks and if they aren't sealed after being etched with acid, you will get rust to return over time. Be sure to keep the tank full if you store the bike a while.

If you properly prep the tank before sealing with a tank sealer, you will get many years more than a cycle or moped will last. Many people who use these sealers get lazy or just don't do it right and give tank sealers a bad name. Many older sealers(specifically that green shit that I am not sure what it was called) didn't stick very well. Years later when ethanol was added to gas they came right out from the alcohol. I remeber my Ninja that I got from a friend cheap had that problem. The fuel line looked like a Chia pet inside. Not Good! I have sealed about 25 tanks and have never had a problem. I even sealed an old Chevy truck tank once.

Re: Epoxy use

where can i buy muriatic acid

Re: Epoxy use

Home Depot, Lowes, any hardware store will have it.

Re: Epoxy use

can you put acid on the chains to get the rust off? how about to strip the rims and other chrome parts?

Re: Epoxy use

Jason Luther /

use wd40 and a wire brush for your chain. muriatic acid will take forever to eat chrome off, and then you have a very toxic mixture of acid and chrome. very toxic

Phosphoric acid is better -

But basically any acid will work to remove rust.

I use white vinegar because it's cheap, won't hurt me, and it can

just be poured down the drain when you're done.



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