The Stovebolt Site Forums The Shop Area Paint and Body Shop Phosphoric Acid Rules!

Absolutely love the results of the small parts being dipped in the H3PO4 purchased from Home Depot.
How can I preserve this bare metal look? I know I could oil, but that would not be maintence free. One or two coats of clear enamel possibly but in the past it has not worked for me. Is there such thing as clear primer? My gandfather used linseed oil and paint thinner on his dads old tools, never saw rust on them, they were not used, but I do seem to remeber him doing it once a year or so.
Thoughts, ideas, all appreciated.
Brett

What kind of parts are you talking about? A clear powder coat may work. http://www.powdercoater.com/faq/#18 It says for brass, stainless etc.

eastwood has bare metal look paint

brackets, u bolts and bolts, shackles, etc. Was considering the lever shocks after blasting. Thanks, I will look into these.
Brett

It's been my experience that phosphoric acid works fine unless the part gets wet. I treated my hood and left it outside (I work in my carport) to prime the next day. It rained that night and I was greeted with a completely rusted hood the next morning and an outline on the concrete where the rusty water has dripped off. Just surface rust but I still had to completely redo the hood.

Other parts treated the same way and stored indoors never showed any signs of rusting.

I'm not familiar with using phos. acid. Do you use it for rust removel or just general cleaning like grease?? Do you use it full strength or diluted?

Spot

Rust only and you can use it full strength or diluted. The 5 gallon container I have say you can dilute up to 10 to 1 & it'll still work on rust...Joe

i used the ospho brand ,put a sprayer right on the bottle and sprayed my cab after i sandblasted. i am doing sections at a time so i wanted to protect against flash rust till the whole cab is done. i'm working under a carport and havent seen any rust....Mark

Once you treat with this phosphoric acid do you have to do a special neuralizing step, hose it down with plain water or just leave it on there? What's the process??

Spot

Spot,
As far as my stuff goes: I degrease a bit, submerge in Phospo (Home Depot at 14.00 a gallon next to the muratic acid/paint department), leave it overnight, pull in mporning, let it air dry and either wire wheel or light sand.
That is where this post comes in, how and can I keep such a nice bare finish.
http://www.flickr.com/photos/dodsonbrett/3301894167/in/photostream/
http://www.flickr.com/photos/dodsonbrett/3301891083/in/photostream/
http://www.flickr.com/photos/dodsonbrett/3301889735/in/photostream/
http://www.flickr.com/photos/dodsonbrett/3301894803/in/photostream/
http://www.flickr.com/photos/dodsonbrett/3302719318/in/photostream/
http://www.flickr.com/photos/dodsonbrett/3302718438/in/photostream/

Cavebull

Darn it Cavebull.....that's impressive!!!!!!!

Do you use it full strength or cut it?

Thanks,
Spot

This is full strength, poured into a rubbermaid tub with a lid. I just put degreased rusted stuff in and if it does not totally submerge, I brush it on and around a bit as I walk to an' fro the garage. I have my front wheel hubs "cooking" right now and will wipe with thinner, prime and paint later today. It is not as harsh as muratic acid, nor does it burn like it either. The iron phosphate coating helps keep rust off. Muratic acid leaves chlorine. I understand the chlorine is what promotes rust, even if you blow it dry with air compressor.
Got the list to thank for this one. Love the archives and search mode.
Brett

Stopped four Home Depot and two Manards on the way home today and they all said they didn't carry Phosphoric Acid. At the last Home Depot the service department girls called all the departments and looked thru their database and couldn't find any mention of it in the store. Soooo, I took off on a walking marathon and about a mile down the isles in the paint department I started reading the labels and sure enough, Behr no.991, Professional Strength Heavy Duty, Concrete Etcher & Rust Remover, contained Phosphoric Acid.
Price was $14 reduced to $3.70 a gallon; they had three left so for $11.10 I brought home the three.
I've tried other chemical rust removers before and been pretty disappointed with them and the cost was out of site. We'll give this a test this weekend and see how it fairs.
Denny Graham
Sandwich, IL

I know how thorough you are Denny, so I'll be anxious to hear the results of your test. Post it here or start a new thread entitled.....

"Phosphoric Acid test results"

Spot

you think it will work as a penetrating type of deal? my door pins are rusted in (along with about every other bolt!) will it break up the internal rust or do you think it will just break up surface rust if i put it on the hinges or around the pins? Corey

Per my find:
Found at Home Depot, Kleen Strip brand and labled Phosphoric Prep & Etch. It's greenish in color, in a translucent plastic one gallon container, with a primariy yellow lable. It too was 14 a gallon. You can see my result but please post your results as I like the 3.7 a gallon. Three gallons would submerge about everything I have and for less than the Kleen Strip brand.

Corey,
As far a penetratingt ype deal, I'm an avent user of propane and PB Blaster. That is how I removed my door pins, among other things. After heat and cooling with PB, simple ping with a hammer and drift pin. Giver a shot let us know.
Brett

Corey41,
with the AD hinges, the easiest way is to cut the pins at the hinge joints, put the strap in the vice, heat up the body and drive the pins out. I don't know aout a 41.

You can buy vinegar cheaper than Phosphoric Acid and it strips rust off parts just as well, it just takes longer. I have a tub of it sitting by the truck and throw rusted parts in and leave them there while I work on other things. Have left parts in for weeks only to go back and find them perfectly clean of even the thickest rust.

BUT! I do like what I'm reading here and will try the acid on smaller parts. I just hope I remember to take them out sooner

Chemist I'm not, so I don't really know the ph of vinegar compared to Phosphoric acid, I'm not even sure what Phosphoric acid is, I haven't taken the time to research it.
But I'm willing to try it.
Woody, I was aging paper to make labels for my old radios and I tried coffee, tea, Ritt, and about everything else I could think of to stain it the right shade without success. Then I stumbled on to this, I soak a fine steel wool pad in a jar of white vinegar for a couple of weeks and it is totally absorbed into solution. Don't know chemically what you would call it but a soak in the tray for my papers and hang them out to dry over night and it really ages the paper to the point that ya can't tell it from an 80 or 100 year old document.
So I know how it will react to Iron.
Acids scare the bajebers out of me, but then again, most things I don’t understand do, like Sweetie Face.
Denny Graham
Sandwich, IL

for what it is worth:
Vinigar is Acetic acid (pickle juice)and weak on the ph scale. Phosphoric (H3PO4) is stronger than vinigar, but not as bad as Muratic. Muatic is also Hydrochloric (HCl). Strong acid, battery acid! Way down on the low end of the ph scale. Phosphoric is not that bad, it is in soft drinks and molasses. I have had my hands in it to get a bolt or nut. Rinse immediatly and still protect eyes. Even a pickle hurts if you get poked in the eye with one - anyway -
Muratic acid blows of hydrogen and oxygen atoms as gas and the Chlorine (Cl)bonds to the Fe+ (positiv iron ion). This causes flash rust as water (H2O) easily breaks the bond and causes (FeO2)iron oxide or rust. Muratic will disolve metal relatively quickly and leaves no protective coating. Oxalic acid will actually disolve metal by "surrounding" an Fe+ molecule. Also, the venting is important as you are off gassing free hydrogen and oxygen.
Phosphoric acid breaks up rust(FeO2) and Phospho (H3PO4) to off gas some hydrogen, oxygen, water, and most importantly, leaving Iron Phosphate (white powder coating left on the metal).
Brett

I have used phosphoric acid in a spray bottle on large areas, doing about a 3'x3' section at a time. Just spray it on, let it sit a few minutes, wipe it down and then hit it with a wire brush on a side grinder. What it does is soften the rust and the wire brush will remove what is loose. Lather rinse and repeat (do it again). It will usually take five or six applications. The last few times you are down to where it looks like shinny metal, but when you spray it the rust in the pits will turn black and show up well. Keep doing it until when you spray it there is no black in the pits. Then do it one more time and rinse like the directions say. I redid most of the body panels on my 60' MGA that way, before I had a sandblaster. That was fifteen years or so ago and I haven't had any rust problems so far. Use a mask.

I used a phosphoric solution for all the pieces that I could submerge. If you don't wash it off the metal will stay protected until you are ready to work with it. Definitely you need eye protection and it makes quite the stain on skin. I reused mine for several years until it grew big crystals.

Cave bull

English translation please

Brad

Hey Brad,
Phosphoric works well. Safe enough to handle, reletively cheap, works quick to remove rust, removes very little of your existing metal, adds a decent rust barrier, a paintable surface, and hard bright metal finish after all is done.
Brett

Is there any fear of hydogen embrittlement using this stuff?

they say some and keep the spoak to a minimum. But evidently not bad. I can not quantify though.
Brett

Well said Cavebull.

I majored in chemistry in college and couldn't have explained it any better myself.

One additional comment......No Smoking while using ANY acids!

Spot

cavebull, i ended up using a torch with MAPP gas and a punch like you said, along with a whole bunch of pb blaster. it was tough but i got them out after a good beat down with a hammer. Corey

The best reason to use Phosphoric is the iron phosphate it leaves behind. Iron bonds with phosphate much more readily than oxygen, so the left over acid salts on the surface retard the formation of more rust from moisture in the air. Other acids strip the iron oxide (rust) from the surface of the metal but don't leave behind a nice coating, so any moisture causes even worse rust because the surface has been cleaned.

It is best to use the iron phosphate out in the open air because you don't want to be breathing the fumes of any acid. Phosphoric acid doesn't have much of a smell and isn't terribly toxic to humans other than the pH, but when combined with the contaminates on the metal or inhaled its bad for your lungs.

Coca Cola contains phosphoric acid as a buffer for the fizz.

Bruce,
That is the beauty of phosphoric acid. After treatment the rust (iron oxide - Fe3O2) is converted to iron phosphate (Fe3PO4) coating. Multiple applications of phosphoric acid may be required to remove all rust and resultant black iron phosphate coting, but so far I have submerged everything for a few hours to expose shiny metal. It too has a powderish coating on it but not black as in the beginig stages of etching. The iron phosphate coating is what provides corrosion resistance but if you remove it you need to paint.
Muratic acid (hydrochloric acid) is bad about flash rusting metal quickly because it leaves no protective film behind.
Corey,
I have been through many a can of PB blaster and torch. Again thanks to the list for the trick.
Brett

Just to clear up a couple points. None of the reactions of acids with iron or rust (iron oxide) generate any oxygen.
Because the density of hydrogen is so much less than air, it will rise so rapidly you are very unlikely to accumulate enough in open air to ignite it when cleaning small parts.
Just because phosphoric (or any acid) is added to Coke doesn't mean it's harmless. It's the final pH and concentration that's important.

Harold,
You are so correct on both accounts. Same can be said of HCL I guess. Just cause the body prouces it, does not mean you would drink it.
Do not want to divert from the beauty of the Stovebolts, simple mechanical objects, and a degree in chemistry is not necessary to enjoy body work. Just be carefull, take proper precautions, use common sense and in the end natural selection will buffer.

Any other products to consider so I can keep such a beatiful finish, so far clear powder coat and Eastwoods metalic finish. Both are very doable for me but can it be as simple a duplicor clear coat?
Brett

This has turned out to be one of the most informative threads I've seen on this site. All too often all we get are replies like "I do it this way" with no reasoning behind it. It's a great advantage to know WHY you do something such as what's been done here.

WOW, Your right.

Directly copied from Wikipedia...

Rust removal

Phosphoric acid may be used by direct application to rusted iron, steel tools, or surfaces to convert iron(III) oxide (rust) to a water-soluble phosphate compound. It is usually available as a greenish liquid, suitable for dipping (acid bath), but is more generally used as a component in a gel, commonly called naval jelly. As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces. Care must be taken to avoid acid burns of the skin and especially the eyes, but the residue is easily diluted with water. When sufficiently diluted, it can even be nutritious to plant life, containing the essential nutrients phosphorus and iron. It is sometimes sold under other names, such as "rust remover" or "rust killer." It should not be directly introduced into surface water such as creeks or into drains, however. After treatment, the reddish-brown iron oxide will be converted to a black iron phosphate compound coating that may be scrubbed off. Multiple applications of phosphoric acid may be required to remove all rust. The resultant black compound can provide further corrosion resistance (such protection is somewhat provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes). After application and removal of rust using phosphoric acid compounds, the metal should be oiled (if to be used bare, as in a tool) or appropriately painted, by using a multiple coat process of primer, intermediate, and finish coats.