Removing rust from a gas tank

[Tony/CT]

I would like to change tanks on my Ambassador. The existing tank is fine on the inside but looks like it has been through a mine field on the outside. The one I purchased looks good on the outside, but when I shake it, I can here little particles of rust in there. I know there is a method of restoring and sealing the inside of this tank, but don't know much about it. Can anyone tell me how this is done, or refer me to someone who might do this. I understand the chemicals involved are quite harsh.

[Dwight Sisk]

Check your PM

[Murray]

Before you go that route and this obviously only works if the tank isn't too bad if you get some ear plugs and a handful or two of steel nuts bolts and washers drop them inside the tank and play shake rattle and roll for about as long as can take it empty out use a magnet on a stick to fish any stuff out that doesn't want to initially (this is why you use steel). Once you've got it reasonable get some rust converter pour it in and work it around the inside of the tank the advantages of this over the sealing method is its a bit more forgiving and can be reworked if it doesn't work properly the first time the sealing kits can be a one shot kind of affair.

[Antietam Classic Cycle]

Some good ideas here: http://www.thisoldtractor.com/moto_guzzi_loopframe_fuel_tank_cleaning_and_coating.html

[Groover]

I want to try the Evapo-Rust method I just read on the link above (one of Charlie's method), but I have a question... Will the tank have flash rust once it's all done? I tried soaking a spare tank I had with 6.5 gallons blend of White Wine and Apple Cider vinegar for about a week, and it did a great job removing the rust - nice and shiny, but flash rush would occur before I could even properly flush the tank with water and dry it. I also tried adding baking soda during the flush to neutralize the acid, but still didn't help. If I use Evapo-Rust, then flush, then rinse with 91% Isopropyl Alcohol, will this also flash rust of does it "maintain" once dry. The vinegar method worked, but the flash rust happening was like a dog chasing its tail. What should I expect when finalizing things with Evapo-Rust?

[Antietam Classic Cycle]

I want to try the Evapo-Rust method I just read on the link above (one of Charlie's method), but I have a question... Will the tank have flash rust once it's all done? I tried soaking a spare tank I had with 6.5 gallons blend of White Wine and Apple Cider vinegar for about a week, and it did a great job removing the rust - nice and shiny, but flash rush would occur before I could even properly flush the tank with water and dry it. I also tried adding baking soda during the flush to neutralize the acid, but still didn't help. If I use Evapo-Rust, then flush, then rinse with 91% Isopropyl Alcohol, will this also flash rust of does it "maintain" once dry. The vinegar method worked, but the flash rust happening was like a dog chasing its tail. What should I expect when finalizing things with Evapo-Rust?

The tank I just did with Evapo-Rust didn't flash rust after the alcohol flush, but then I did fill it with gas and slosh that around almost immediately afterwards.

[Groover]

Ok, thanks for the reply. Would it be safe to do this on a freshly painted tank, or should I do it before. Before is my guess, just wondering how harsh (or gentle) this stuff is.

EDIT: Found a good video that pretty much answers my last question. https://www.youtube.com/watch?v=3RWj1X4-_RI

I'm sold. Thanks again!

[Perazzimx14]

 Milkstone remover is what I have been using wild great success and cost effective at $10 a gallon which is enough to clean a tank.

[Kiwi_Roy]

Clean with Muriatic acid used for etching concrete.
Finish off with a product called Rust Mort, it leaves a hard finish that looks like grey primer paint.

[Antietam Classic Cycle]

Ok, thanks for the reply. Would it be safe to do this on a freshly painted tank, or should I do it before. Before is my guess, just wondering how harsh (or gentle) this stuff is.

Evapo-Rust doesn't seem to effect anything other than rust. No problem with paint, decals, etc. Don't know what's in it, but it's very "gentle".

Milkstone remover is what I have been using wild great success and cost effective at $10 a gallon which is enough to clean a tank.

Had planned to use milkstone remover, but nobody around me carries it.

[jetmechmarty]

I have experience here and I'm about to get some more.  I've done electrolysis, phosphoric acid, mechanical removal, and Metal Rescue.

The first question in deciding what to do is how bad is it, and will I end up lining it?

If it's just a few little spots and you want to remove it and drive on, there's no doubt using Metal Rescue or Evapo-Rust is the way to go.  The factory tank lining will be unharmed and the rust will be destroyed.  There's no better way.


If it's bad rusty, you can remove the bulk of it mechanically.  Harbor Freight sells resin rust cutting media.  I put about 2.5 lbs of it in the tank then put it in the clothes dryer packed full of pillows and sleeping bags, then let it tumble the media (heat off) for a couple of hours.  The resin media won't cut good metal.  Whatever you can't dump out at the end, you can suck out with a shop vac.


Removing the rust with electrolysis works, and it's pretty safe.  I was left with hard black what I believe is iron phosphate (somebody correct me here).  It's harmless, but I don't care for it in there.  It won't rust there again.


For a bad rusty tank, phosphoric acid is cheap and easy.  I add about two cups of acid to a five gallon tank full of water.  You can fill the tank with vinegar as an alternative, but it's slower.  Two to two and a half cups of acid is going to do the job in less than 48 hours or even overnight.  It's going to etch everything it comes in contact with.  Once the acid is drained, you have to neutralize it with baking soda solution, then be prepared to do something with it, even if you just coat it with fogging oil, because it's going to flash rust.  It's probably best to put a liner in it.


My choice is an epoxy liner.  The down side is that I have no clue how to remove it, should it become necessary.  Other liners can be removed with acetone or paint stripper, depending upon the liner.  I have removed a failed liner and it's not a lot of fun.

Web Bike World has a review of this stuff available if you're interested.

 

[jetmechmarty]

Evapo-Rust doesn't seem to effect anything other than rust. No problem with paint, decals, etc. Don't know what's in it, but it's very "gentle".

I believe that and Metal Rescue are chelating agents.  They won't touch paint or good metal.  I've seen folks use molasses the same way, but I think it may have an acid component.  I'm going to try it, but probably not in a tank.  The downside is that it's slow as molasses.

[erik_w]

I used a Kreem tank saver kit to save a tank that had pinhole leaks due to rust. the kit included both rust remover and sealer. It wasn't hard and I was very satisfied with the results .

[Groover]

Great info. I think in my case the Metal Rescue or Evapo-Rust will work well luckily. The inside of the tank doesn't look too rusty, just a few light sports here and there, so knowing it won't mess up the factory lining is definitely a plus.

I think vinegar does eat the factory lining.. I know it completely ate up my petcocks. I'll have to post a pic later.

The vinegar also ate up the paint where it was already chipped - that was to my surprise, luckily it was just a spare tank I was playing around with. All the damage happened after about 3 days, so for short term, it should be ok - I would not trust it however. It does remove rust though!

[jetmechmarty]

I think vinegar does eat the factory lining.. I know it completely ate up my petcocks. I'll have to post a pic later.

Vinegar is acid.  It works, just like phosphoric acid, muriatic acid, milkstone remover, etc.  You can probably remove rust filling the tank with Coca-Cola as it has phosphoric acid in it.  It's just a matter of how much acid and how long it takes.

Evapo-Rust and Metal Rescue have no acid content.  Safe!  They won't touch good metal, paint, etc.  I'm making assumptions about Evapo-Rust based on their advertising and what others have said.  I have direct experience with Metal Rescue.  It is now available at Home Depot.  Good stuff!

[normzone]

////Harbor Freight sells resin rust cutting media.  I put about 2.5 lbs of it in the tank then put it in the clothes dryer packed full of pillows and sleeping bags, then let it tumble the media (heat off) for a couple of hours. ////


That's brilliant, I wish I'd thought of that. One of those things you do when your wife is elsewhere, just like baking parts in the oven prior to painting them.

[Antietam Classic Cycle]

I used a Kreem tank saver kit to save a tank that had pinhole leaks due to rust. the kit included both rust remover and sealer. It wasn't hard and I was very satisfied with the results .

I wouldn't use Kreem tank liner if it was the last option available on earth. Seen too many failures. IMO, there are much better products - POR-15 and Caswell Epoxy Gas Tank Sealer (my favorite) being two.

[erik_w]

I wouldn't use Kreem tank liner if it was the last option available on earth. Seen too many failures. IMO, there are much better products - POR-15 and Caswell Epoxy Gas Tank Sealer (my favorite) being two.

I see! I have only heard good things about it, what failures have you experienced? As I understand the trick is to make sure that you let it dry a bit between recoatings to make it thick enough.

By the way, I have also used Coca-cola to remove rust from nuts and bolts; drop them in and wait for a day or two, then you can wipe the rust away with a rag! Does leave a miscoloration where the rust was - but quite cool that it works!

 :bike

[jetmechmarty]

I see! I have only heard good things about it, what failures have you experienced?

By the way, I have also used Coca-cola to remove rust from nuts and bolts; drop them in and wait for a day or two, then you can wipe the rust away with a rag! Does leave a miscoloration where the rust was - but quite cool that it works!

 :bike

I've had two tanks with failed liners.  Both lifted and were grey in color.  Since I didn't install them, I can't be certain it was Kreem or that it was done properly.  Cleaning up the mess was a PITA.  Read about one of them here:  http://xs650temp.proboards.com/thread/17274/failed-tank-liner

The active ingredient in Coca-Cola is phosphoric acid.  A stronger solution will work much faster.

[Antietam Classic Cycle]

Just was passing it along for a data point, and not heaven forbid, a recommendation/endorsement!

I think I will go and lay down!

Sorry if I "ruffled some feathers" with my opinion. I see a lot of old bikes in my line of work and all but one that had failed tank liner were done with Kreem. My own experience was less than stellar - of the two tanks I personally did, both failed and not for lack of following directions or preparation. Unless they've changed the formula in the last ten years, it's just not the best choice, in my opinion.

Switched to Caswell which is much easier to apply and is (in my experience) much more durable. Going on seven years in my garden tractor tank which sits with 10% ethanol fuel in it year round. Zero degradation of the liner.

[mgmark]

Had planned to use milkstone remover, but nobody around me carries it.

I buy mine at Tractor Supply. Works well to remove rust from chrome parts also.

I also agree the Caswell liner works very well. It will even plug a leaking tank with actual holes in it.

[oldbike54]

If I had feathers I could fly.

:-)

  :D :D :D :D :D
  If I had a tali I'd wag it ?  ;D

   Dusty

[Antietam Classic Cycle]

I buy mine at Tractor Supply. Works well to remove rust from chrome parts also.  

Tractor Supply(s) here don't carry it and won't order it for me. Southern States and other "farm" supply places didn't have it either. Evapo-Rust in the gallon size was on the shelf at the local TSC, so I bought that instead. Glad I did, it works very well.

[rodekyll]

I bought a quart of POR-15 tank liner to treat my trike fuel tanks before I put them in service.  They have some sort of lining in them from the factory, but I've braised on them and probably ruined it at the bung holes.  They're new, so they're essentially clean inside.  Any hints on prepping them?

I cut up a couple of loop tanks last month, one that had been lined and one that had not.  They were both rusted out.  The unlined one had rusted randomly through the bottom seams and bottom proper and was retired.  The lined one was leaking along the seams around the filler port.  The liner had been applied to stop rust through and leaks in the bottom, judging on how the material was embedded in rusty (but well sealed) spots.  The filler leaks appeared to have happened after the liner was installed.  I think the installer didn't pay good attention to either prepping or coating the top.  Otherwise the liner seemed to do its job, possibly for a very long time.  It was quite thick in some places and like I said, the top seemed neglected.  I think it was a home-done job.  I have no idea what brand it was, but it was charcoal gray and stank like plastic when I put the grinder to it. 

My point is that home-kit liners can work, attention to detail is important, and something like the dryer idea to distribute it evenly will improve the overall result.

[Perazzimx14]

Tractor Supply(s) here don't carry it and won't order it for me. Southern States and other "farm" supply places didn't have it either. Evapo-Rust in the gallon size was on the shelf at the local TSC, so I bought that instead. Glad I did, it works very well.

Let me know the next time you'll be above the Mason-Dixon line and I'll have a jug of Milkstone remover waiting for you.

I have also been talking with a couple of my water treatment contractors to see about commercial rust/scale removers and the art of the possible of scoring some "leftover" product inexpensively.

[Antietam Classic Cycle]

Let me know the next time you'll be above the Mason-Dixon line and I'll have a jug of Milkstone remover waiting for you.

I have also been talking with a couple of my water treatment contractors to see about commercial rust/scale removers and the art of the possible of scoring some "leftover" product inexpensively.

Thanks. Still have that taillight for your T3 (actually two to choose from) here at the shop.

[jetmechmarty]

I see a lot of references to Milkstone Remover.  What is special about it?  It is 56% phosphoric acid solution and 44% surfactants, dye, and water.  What am I missing? ???

[Perazzimx14]

Thanks. Still have that taillight for your T3 (actually two to choose from) here at the shop.

Once the weather warms up a bit I'll mule a jug of milkstone remover across the border and trade you for a taillight.

[Perazzimx14]

I see a lot of references to Milkstone Remover.  What is special about it?  It is 56% phosphoric acid solution and 44% surfactants, dye, and water.  What am I missing? ???

It's cheap and it works.

[jetmechmarty]

It's cheap and it works.

I'm sure it is, and it does. (Milkstone remover)  But, if it's not available, phosphoric acid is very cheap at lots of places, like my local hardware store.   ;-T