does anyone know...

pea shooter /

Where I can get some phosphoric acid? I am very annoyed because I have been looking for about a week calling stupid companies who sell it in 55 gal barrels only! I need some to clean out my gas tank cause CLR doesn't do shit! I think I am going to have to get a kreem kit, but I really dont want to just coat the inside of the tank. I want to completely clean it. But if it does come to that, does anyone know how much a kreem kit costs?

Re: does anyone know...

Have you tried gasoline with rocks?

Re: does anyone know...

pea shooter /

It is an in frame gas tank.

Re: does anyone know...

Dood, Just based on your previous thread, I'd really think twice before opting for the Kreem Kit (about $30.00). It sounds like all you have is surface rust. And being an in-frame tank, lining it with the Kreem kit will be a MAJOR pain in the ass. Not impossible, but more of a last resort situation.

If it were me I would work out a way to use a pulley to hoist it in the air so that you could rotate it around more easily. Then use something like Naval Jelly (thinned out). Have you tried a hardware store? I think if you find a knowledgeable salesperson and explain what you are trying to do they should be able to hook you up.

Also, have you used the search feature here yet and typed in "Rust" and "Tank" or "Tank" and "Clean"? I know this has been covered thoroughly many times before. Good Luck!

Re: does anyone know...

pea shooter /

I hope navel jelly is stong enough, they always sell weak ass shit for "safety reasons". But if you say that you need to dilute it i guess it will be strong right?

I think I will try that in place of the CLR and if that doesnt work, I will go for the kreem kit. I dont mind actually using the kreem kit difficulty wise. I mind it not being as good as a clean tank. So if anyone knows, is a lined tank just as good as a cleantank? Or should I try not to use the kreem kit as much as possible. Because if it doesn't matter (aka the lined tank is just as good as a normal tank) I think I will go for the kreem, even if it is harder, at least it works :-)

Re:Phosphoric or Muriatic/Kreem Q's

They sell muriatic acid at most hardware stores for the main purpose of scrubbing old masonry..... (used to be a mason tender---yuck)

pretty cheap, nice and strong, and comes in quarts or gallons.

Just an idea, and this may be the dumbest thing ever posted here---

Why not Drano? or one of those toilet acids? OBVIOUSLY you don't want that crap in the engine......but as long as the tank is disconnected....

I dunno--- I would stay with the first two.-- the drano idea was just a "pop into your head" idea.

I have a friend who has a harley, and has done a few kreem coatings.

he said it's NOT a pain on frame welded tanks... that the reactive agents stick to the metal perfectly.... that he had no trouble and said it was easy even with a non-removable tank.

I've never done it---- I've heard opposite answers from different sources... and I trust both sources...! tough call.

I kept asking--- if I remember he said if you can "Mix" "pour" "wait" and "drain" that you couldn't screw up. "If you can mix epoxy, you can coat your tank..." more like famous last words......

Now, Sully, he has a few loose screws, but he does know harley's very very well.

So, why shouldn't we use drano to clean a tank, and is my harley frind right or wrong about the coating kits being easy to use on frame welded tanks?

Re:Phosphoric or Muriatic/Kreem Q's

pea shooter /

I really have no problem with kreem coating the tank. My cousin and I have already put in some crappy spary and picked up the entire bike and shook it. Mopeds arn't very heavy.

I was just worried that a kreem kit wouldn't be very good, or it would be a temperary solution. But if not I might as well do it. But since you say muratic acid is available at most hardware stores. I will just pick some of that up while I am returning the 20$ worth or CLR (does not contain phosphates, WHICH IS WHAT WE WANT!) to lowes. Ill do the muratic thing, but how long should I keep it in the tank? I don't want to have to scrub it because that is a complete pain, so will the acid completely do the trick? But the muratic acid is the final straw. If it doesn't work I'M GOING KRISPY KREEMY!


Use $5 worth of molasses...

and no I ain't kidding...

..... a byproduct of sugar refining called 'treacle' is a known rust remover for ferrous materials (iron and steel).

Treacle is also the key ingredient in a much more expensive commercial product called "Rusteco"... (that you may find at your hardware store).

It takes a week or two.. but its dirt cheap and eats rust without eating good paint.

Here's an acount of it.......


I read an internet article about using horse "feed grade" molasses mixed with water as a rust remover. I thought "yeah right", but decided to try it anyway. I mixed molasses I got at the feed store with water at about a 1 to 7 ratio. I stuck a hopelessly rusted Honda XR70 tank I got from a friend into a 5 gallon pail of this mix to see what would happen.

After about a week - no progress at all, I figured it was a bunch of crap, but since there's no work involved and the tank doesn't need to be anywhere I decided to let it sit. So today (about 2 weeks from start)I went out and checked it again.

The mix looks and smells gross! Past three days have been pretty warm here and it's starting to ferment, stink, and "skin" over - Blech! But when I pull the tank out of this "cesspool" and look inside, Lo and's a thing of beauty! The inside of the tank sparkles, only a few rust spots left, and they are soft and disappearing. All of the not-so-nasty areas of rust are completely gone and the paint only flaked loose where it was barely sticking to begin with (The original Honda red paint appears unharmed). Keep in mind this tank was considered "junk" and unsalvagable when I got it. I'm going to give it another week or two to get the really bad spots.

This method has produced the best results of the 5 I've tried on tanks and really works beautifully (as long as you aren't in a hurry)- No "etched" look either, like with Muriatic acid. The metal really shines. It cost me 5 bucks for about a gallon and a half of this molasses (I had to buy enough to make it worth the feed store owner's effort) I still have a lot left over.

I think the secret is you have to let the mix sit long enough to "get stinky" and it was too cold outside before for that to happen.

The "Rusteco Super Iron out" worked to an extent, but not as well as this, and its way more expensive


So there you go... $5 worth of molasses and 2 or 3 weeks wait would do you.

Re: Use $5 worth of molasses...

Fredder, you're an f-ing genius. Well done.


Re: Use $5 worth of molasses...

please... don't give me credit for thinking this up.... I didn't.... I only heard it on the net about 3 months ago... and its been done by two people I trust.

I LUVVVV the fact that its so cheap and simple.

I also LUVVV the fact that somebody has kept this old technology alive... modern companies would have you think you have to buy their overpriced stuff... and its 'magic' ! ... ooooh!

I don't know if pea shooter has the patience to wait 2 or 3 weeks though... and if he's a city boy... he may have never heard of a feed store.

peashooter... you can also buy phosphoric acid at farm supply stores... they sell it to dairy farmers and food processors... who use it to clean and wash their stainless steel processing equipment.

Re: Use $5 worth of molasses...

pea shooter /

my pateince sucks... i dont want to waste the summer w/o riding my 1st moped. and I'm 14, so its twice as exciting as normal seeing as it is my transportation. I think I will go with filling the tank up with muratic acid... but does anyone know how long I should leave it in there?

Re: Use $5 worth of molasses...

How about saying screw it and just buy an inline fuel filter....How rusty is it?

Re: Use $5 worth of molasses...

Unless it's horrible, and inline filter would be a temp fix....

I don't know how much Muriatic acid to use, there, Pea. wish I could help.

Like suggested earlier .... take a similar piece of rusted metal and put it in the diluted muriatic acid to figure out how much and how long

I know you're probably thinking "why cant I buy a whole gallon of the muriatic acid and fill 'er up? Well, i just don't know. Maybe you can??

And, Muriatic acid might not be the best-- others keep saying phosphoric--- I only suggested muriatic because I used it as a mason tender to scrub brick--- it IS a powerful acid...acid eats rust.

Have you done the forum search yet-- man... Fred's idea is the best but there have been a LOT of posts on this subject.

Do you have any Q's about how to use forum search?

good luck, Pea-Man. It's a crappy weekend here in new england--- if you're on the east coast---- get to work on the moped's tank.

Re: does anyone know...

merlin311 /

pool store!pool stores have muratic acid!i have four jugs sitting in my garage for my inground pool just tell em its for ur pool...

Re: Use $5 worth of molasses...

pea shooter /

yeah first i wanted to try phosphoric acid but I couldn't find it ANYWHERE! I got CLR but it suxors. So I'm going for the muratic, I guess I will just have to test it on some similar rusty metal. I also am going to get fuel filters for the ped after I clean the tank (just to put it in tip top condition) but does anyone know what size fuel filter a 1978 Puch Maxi will take?

If the Acid+fuel filter just wont work I will go with kreem, which shouldn't be a problem cash wise or putting in the tank wise.

Thanks guys.

P.S. If you read this and do have an idea of how long to leave muratic acid in the tank, please post. Thanky.

:-) Pea

Re: Use $5 worth of molasses...

Matt Wilson /

I used muriatic acid to clean 2 gas tanks a puch and a peugeot.

I used straight acid and let it sit for 1 hour. This seemed to dissolve all of the rust.

However, I did have some problems with the gas tank in the peugeot rusting back up again. It is not nearly as bad as before, but it sill has a little surface rust. I installed an inline filter and I haven't had to clean the carb yet. The puch had no reoccurring rust

The biggest problem that I had with this method was that I had tons of rust particles left in the tank after I drained it. I hooked up a pressure washer and ran water through it for a full hour before it was runnning clear. I think that the rust reoccured a little while I was flushing the tank. Ideally I think you would want to flush with gas, but I couldn't just pour 50ga of gas into the sewer:)

Also you must remove your petcock first. Find some other way to plug your gas tank. If it has external threads try and get a dome nut, and if it has internal threads get a plumbing fixture and link it to a pinched fuel line.

Muriatic acid will eat through your petcock and cause it to leak


Danger Zone Dude

Hey Pea,


Just to chime in... I too used muriatic acid about 50/50 with water and let it stay in my puch over night (although I did add more acid to the tank to help it along). You must remove the fuel petcock prior to the project so you can get a good drain out. I used a plug of some sort that held well in the hole(a hose that fits over the threads with a pinch spring clamp would do and will help keep the draining s in a pan). After the acid is drained I flushed it out well with a garden hose. I put a qt. can of acetone( HIGHLY FLAMMABLE, DRY GAS MIGHT BE SAFER?) in the tank to cut any varnish and help dry out the water. After draining that I snaked a compressed air hose in and let it run for a good while to dry things out.

I caught all the draining-s. diluted the acid and poured it down the drain to the city sewer. The acetone I put back in a can for future de-greasing jobs.

If you disassemble your petcock you will probably see that the small holes that direct the fuel are plugged solid and maybe the rubber gasket in there is deteriorated. you will need to service or get a new one.

A motor cycle shop will probably have a nice little clear plastic fuel filter with a brass filter stone inside that you can fit between the petcock and carb. Get a foot of fuel line from the cycle shop too.


After that I have kept fuel topped off in the tank to keep re- rusting down, especially when it sits for a period.

Have fun.

Re: Danger Zone Dude

Ron Brown /


Walter has said enough, listen too him.

NO ONE can tell you how long to leave the acid in the tank. you are the only one who can see how rusty it is. This is a repeat.

A Kreem kit requires that you clean all the rust from the inside of the gas tank first, so there is no advantage there, except that they provide the acid.

Muriatic acid will work just fine, metal tends to rust almost immediately after using it and does not if you use phosphoric, but I have used both and if you get gas/oil back in the tank, you will be fine.


Re: Danger Zone Dude

pea shooter /

so I should use muratic, but then immediately after I flush it out with water, (then use my water remover i bought to get out all of the water.) I should fill it up with gas fast. After about week will the re-rusting stop? Will it ever stop? Or will I have to always keep it filled with gas? That would be a pain....

Re: Danger Zone Dude

Ron Brown /

2 stroke oil is very sticky, as soon as it coats the tank your rusting will stop. As long as you a using the ped regularly, the gas will splash around enough to keep it from rusting.

If you park it for the winter and have condensation problems in your area, make sure it has a full tank.


Re: Danger Zone Dude


You're obviously concerned with :

1. not damaging your ped

2. getting it right

I think, at this point, you've got plenty of correct, accurate info. All you need is a nice day and trust your common sense.

You will not need to "keep doing this" as ron said. It is a good idea to keep ther tank full or at 3/4ths on ANY vehicle..... even on a plastic tank, that extra air space will get condensation....

It's not a major pain in the ass to keep your moped nearly full.... the sloshing of the gas will prevent much of the surface rust.

In maine, we have warm days and cool wet nights. my moped is on an external front porch... a roof and windows, but no door.... if I don't fill my tank, I notice the water affecting the performance.

In our car too--- run it for a week or two in the spring or fall (even summer for that matter) on 1/4 of a tank.... before long you're sputtering and trying to run on some watered down fuel.

Sandblasting wasn't mentioned much... but if you have a friend who does body work... or owns one.... that's a decent option.

It's awesome that you're so concerned with getting it right the first time.

before long, we'll be making YOU tell the newbies how to remove the rust... so be careful how much you learn here.

Have fun w/your project.

rotten, cold and rainy in northeast,


Last question

pea shooter /

ok i got all the stuff and I am beginning the procedures but i have one last qeustion.

If i get the kreem kit and line my tank, wont that technically stop it from ever re-rusting. That would be cool, then I wouldn't have to worry about it re-rusting if I ever stored it.

Thanks for all your help everyone!!!!!!!

Pea shooter

Re: Last question

Ron Brown /

"Technically", this is true. However, if you screw up the Kreem kit by not getting all the rust out so it does not stick, you are in deep doo-doo. I have several tanks I have cleaned (also one I Kreemed), without any re-rusting problem.


Re: Last question

david f martin /

Any VW shop can supply you with a small clear plastic inline filter for about 3 bucks. Definitely go with a clear filter, so you can tell when to replace it.

I cleaned the tank for my '67 bus. Put a bunch of nuts and bolts and nails in it, took it to the car wash and sprayed some engine cleaner in it, shook it up and drained it several times till it came out clear.

Had to replace the fuel filter frequently a few times, now it's as good as new.


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