Topic: Phosphoric Acid

[CBXJOHN]

Thank you for the tip on treating a fuel tank with Phosphoric Acid, I did my 1988 Honda Hawk GT this past weekend, I can say this, it works amazing!

john

[Duanob]

Sounds great but can you link the tip in your post?

[RedDawn]

http://forums.sohc4.net/index.php?topic=21464.0 

Steel wool (or even scotchbrite pads) will scratch chrome, and it's a lot of hard work. Get some phosphoric acid and add water at 5 parts water to 1 part acid and dip the rims, fenders, grab rails, blinker stalks, exhaust pipes, handlebars, chain guards, seat bases etc etc in the solution for a few minutes then just pull it out and rinse with clean water, and you'll think it just rolled off the factory floor, no scrubbing or polishing required! Cheers, Terry.

http://forums.sohc4.net/index.php?topic=31053.0

The Home Depot's here in MD are now carrying phosphoric acid in their paint stripping section.  Product is called "Prep and Etch." It is a gentler, more forgiving product than muriatic acid that takes overnight to work but leaves a rust inhibiting coating on the metal.

http://forums.sohc4.net/index.php?topic=31970.0

did this, this weekend. Watch out for flash rusting. I read up on this a while back and it seems that the best acid to use is phosphoric acid as it will remove the rust while leaving the metal in a state that is somewhat inhibitive to oxidatation/rusting. I have done some small parts in phosphoric acid and noted no flash rusting.

[tbpmusic]

I get it from Tractor Supply or Farm&Fleet.
Called "Milk Stone Remover" (MSR), it's about 70% phosphoric acid, dyed orange.
Dairy farmers use it to clean out their stainless lines and pumps, etc.

I mix it by half with water, process nearly everything through it.
Hell on rust, won't touch your chrome, wonderful stuff.
Not nearly as "hot" as hydrochloric acid based stuff, much safer.

Flash rust will start almost instantly in this part of the country, so I always do it right before I rinse with water, blow dry, rinse with acetone, then primer or paint (or put RedKote in if it's a tank).

[The_Crippler]

Ooooooooh...this might be just what the doctor ordered.

Sorry to rehash anything that might have been in the linked threads, but is this just to pretty up chrome with a few spots of rust on it, or can this handle something with a far amount of surface rust?

Also, what did you mix it up in?

[tbpmusic]

Ooooooooh...this might be just what the doctor ordered.

Sorry to rehash anything that might have been in the linked threads, but is this just to pretty up chrome with a few spots of rust on it, or can this handle something with a far amount of surface rust?

Also, what did you mix it up in?

I have a 5-gallon plastic pail (safe), and a regular ol' 40 quart cooler full of the stuff. I use whichever size is needed.

It will remove ALL rust, no matter how deep or extensive.
The reason it makes chrome look "better" - it's just that all the rust is gone. There may be extensive pitting in badly rusted chrome once you're done - all the missing rust leaves pits.
If that happens to me, I just rough up the chrome with a palm sander, spray on some etching primer, then some "build-up" primer, then sand a little and paint/clearcoat.

The photos here will show a CB450 model, nearly every part on it was MSR'd and painted, even chrome fenders, etc.......

http://home.comcast.net/~tbpmusic6/450site.htm

[The_Crippler]

I guess another part that worries me is, can the parts be "over cooked"?  Or, can you soak it forever, because the chemical reaction only effects iron oxide?

[tbpmusic]

I guess another part that worries me is, can the parts be "over cooked"?  Or, can you soak it forever, because the chemical reaction only effects iron oxide?

Of course you can't soak it forever.
Anywhere from several hours to several days, just check on things once in a while.

[The_Crippler]

Cool, thanks.  Yeah, the "forever" was an exaggeration - but "a few hours to a few days" is a lot longer than "Sit there with a stop watch and get them buggers out," which is what I feared.

So, basically, drop them in, go do other stuff and check on 'em after dinner.

[Brown Bomber]

Keep the MSR away from spokes, and other zinc plated parts, it will eat it up. I made a trough for dipping a wheel that had rust inside the rim, and while it did a good job on the rust, it did a number on the spokes, and nipples. Though the chrome on the rim was a bit dull before, it was definitely duller afterwords. I wouldn't worry about it hurting good chrome, but I won't put it on some that is a little dull.

[Rob M]

Anyone on here try the electrolysis method it is safe and effective and for me the best part you don't really have to buy much in the way of chemicals or parts. Just a battery charger and some alcohol to dry up after. If it's already been gone over on this forum I won't rehash it.  I just had pretty good luck with it.

[tangopeter]

The electrolysis method? Do you have a link or a description?

[Kong]

I have seen the electrolysis method used, but someone else will have to fill in the particulars.  Basically there is some sort of powerded soap, borax or something like that, that you mix with water and then immerse your part.  One electrode from the charger is connected to the part and the other charges the liquid (I think its the Negative that goes to the part) and then you run the charger at 2 amps or something like that.  It removes all rust.

That said, and someone else will know a lot more about it than I do, obviously - but there is something more important.  If you are using any of these methods that use an acidic bath for rust removal you need to make very sure that you only have one part in there at a time and that the part you have in there doesn't have anything still bolted to it that might be made of a different type of metal.  If you don't get all the parts off and have two different metals in the bath at once you are going to do damage.  Basically what you will have created is a battery (dis-similar metals in an electrolite solution) and there will be metal transfer from one surface to another - in short you will be corroding one piece and plating the other.  So be careful to completely disassemble any parts you intend to clean up using either method (the battery charger method will be even worse than the acid bath method if you try it).

[pidaster]

Electrolysis uses water and sodium carbonate mix. Use about a 2amp manual battery charger with the negative lead attached to the item you are removing rust from and the positive lead to the sacrificial metal that the rust will now go to. I usually check it every few hours and sometimes have to change the solution and clean the sacrificial metal up.

[tangopeter]

Okay, thanks, I might try it. Any tips about the amounts/ratios to be used?

[pidaster]

I think it was one tablespoon per gallon.

[Duanob]

Thanks for all the info. I'll be cleaning my tank this weekend before bondo and paint.

[SOHC Digger]

Any suggestions on a good place to pick up Phosphoric Acid in the Chicago area?

[MCRider]

Any suggestions on a good place to pick up Phosphoric Acid in the Chicago area?

PA is the main ingrediant in most "RustNeutralizer" type products at Loews, etc.
http://www.theruststore.com/Rust-Remover-Comparison-Chart-W22C2.aspx

http://www.chacha.com/question/where-do-you-get-phosphoric-acid

It is also in Pepsi Cola, though fairly diluted. A 2 liter bottle may work.  

And as TBPMusic mentioned, MSR is available, 70% Phos Acid
http://www.tractorsupply.com/livestock-equipment/cattle-handling/dairyland-milkstone-remover-acid-rinse-2214079

[Duanob]

One thing read the bottle! All rust removers use something different make sure it says phosphoric acid. Also whoever siad it doesn't flash rust is wrong. It's not bad but it still does. I had to put a bit of marvels in the tank and seal of the holes and shake it around. It does work.

[db22]

One thing read the bottle! All rust removers use something different make sure it says phosphoric acid. Also whoever siad it doesn't flash rust is wrong. It's not bad but it still does. I had to put a bit of marvels in the tank and seal of the holes and shake it around. It does work.

I used Prep and Etch from Home Depot, which is a PA solution, and it works really slick.  As Duanob says, it does flash rust, and Marvel Mystery Oil works as a gas-compatible rust inhibitor.

[cafe550]

this acid you guy talk of will it hurt the paint on the tank

[db22]

this acid you guy talk of will it hurt the paint on the tank

My tank is just primed right now, but it didn't hurt the primer -- just left a barely-noticeable stain.  Test it on your paint first, to be sure.

[tbpmusic]

this acid you guy talk of will it hurt the paint on the tank

If you wipe it off right away, there will be no damage - remember you dilute the stuff at least 2:1 before use.
If you let it sit on the paint for a few days, it probably will go at the paint.
Probably more of a danger getting the tank sealer you choose on the paint.........

I usually paint the part (or RedKote the tank) immediately after treatment and washing/drying - if not, I swish around a little heavy 2-stroke gas mixture (from my weed-whacker), this stops any flash rust.
But I try to seal the tank immediately - if you put oily stuff in it, you'll have to clean it real good before sealing, and that means another $20 can of acetone, which ain't friendly to paint or the wallet......

[lucky]

Phosphoric acid turns iron oxide(rust) into iron phosphate which is inert.

Very good to use before painting or sealing.
If you are using epoxy paint remember that many epoxy paints contain 25% phosphoric acid. That is what makes it stick. It etches the surface and gives the surface a tooth to adhere to.