phosphoric acid rust removal field test

[sgallaty]

I bought a siezed engine from a friend that ended up having a great deal of rust in one cylinder and a ring in the other.

I'd read different derusting methods and there was only one that appealed to me which was phosphoric acid rust removal.

The method is to create phosphoric acid with a 9:1 ratio of molasses to water, and then submerge the piece in the solution.

It is also available in larger concentrations commercially. http://www.42gpw.com/acid.html

--

Experiment -

The experimental piece is a set of cylinders which significant rust on one cylinder and light surface rust on both.

Method -

Submersion in a solution of 9parts water to 1 part molasses, combined with nonabrasive physical debris removal and solution agitation.

Chronological Diary

Started experiment on 7/12. Created solution and immersed head.

Observations :

even after rinsing, the head had a great deal of foreign material and oils adhering to it. This caused pollution of the solution.

solution did not begin to react for approx 12 hours after immersion. did not test, but suspect that the phosphoric acid is not formed immediately.

It has a moderately unpleasant odor

Notes :

For the next experiment, we'll soda blast to thoroughly clean all parts prior to immersion.

for best results, solution should be premixed 24 hours prior to immersion.

when process is underway, bubbles (presumably oxygen from the FeO Iron Oxide breaking down and the formation of FeP2/FeP3 Ferrous Phosphate.

Condition of piece on 7/12

 

[sgallaty]

7/14

I just threw in three small pieces which had rust on them. Two chrome tops from a set of 34's, and a gas tank lid. The gastank lid has big cancer spots.

Within about an hour the surface rust on the two chrome carb tops had turned partly black, and those parts wiped off the surface with a slightly slimy texture.

the left hand cylinder has come completely free of any rust that I can feel. The cylinder is smooth and there is no trace of the ring of light rust from the piston rings.

When I stuck my fingers into the cylinder, the parts of the cylinder that were rusted earlier had a slimy feel to them and my fingers wiped a black powdery substance off of the walls of the cylinder. That substance is ferro phosphate.

As of right now, the larger chunks of rust are slowly deteriorating. They are softening to the point where I can scrape portions off with my fingernail. The pieces which come away are chunks of granulated black mixed with unconverted iron oxide.

When the mixture is operating correctly, bubbles form over the parts that are reacting.

 

[bluebikerblan]

For what you're doing I'd recommend:

Evaporust: http://evaporust.com/evaporust.html

Rustblast: http://www.kbs-coatings.com/prep-products.html

MSR Old reliable & safe to use milk stone remover available from a variety of sources including most Tractor Supply Stores. ( Dilute phosphoric acid solution)

Evaporust.....uses a cheleated phosphate compound to reduce the iron oxide and is very safe, clean and green to dispose of......love it for what you're doing.

Sounds like you've got your head around the chemistry. As to Molasses or Coca-Cola for that matter it's the phosphoric acid (active ingredient in both) that's doing the work, might want to avoid all the sticky sugary mess and clean up??? though neutralization afterwards does make some sense.

Rustblast on a tank you'll be relining is the nuts btw. leaves a great etched & primed surface!

Best, Blue

 

[grepper]

I'll be watching this thread...
For a few years I've used 1 part Muriatic (diluted phosphoric) acid 2 parts water to clean rust off of parts and the inside of gas tanks. I always check it regularly because when it's done with the rust it will start to eat the steel. I always rise the parts with water and baking soda (to neutralize the acid) and dry it right away and either paint or cover in oil right away, or I'll get flash rust. As for aluminum, the acid will eat that right away.

I've used oven cleaner (that stuff than comes in an aerosol cans) to clean engines. It eats the grease and leaves it super clean, but will leave the aluminum with a haze, that can be brushed off with a mild wire brush. Of course, not while the engine is in the bike. The oven cleaner will eat the paint on the frame and damage other parts.

 

[sgallaty]

I specifically chose this method for several reasons : It's gentle, and cannot affect the unrusted metal in any way, it leaves a protective coat when the piece is removed from the solution so no flash rust, the solution is nontoxic and can be dumped on the lawn when finished.

It's a slower process but I am in no hurry.

 

[bluebikerblan]

I'll be watching this thread...
For a few years I've used 1 part Muriatic (diluted phosphoric) acid 2 parts water to clean rust off of parts and the inside of gas tanks. I always check it regularly because when it's done with the rust it will start to eat the steel. I always rise the parts with water and baking soda (to neutralize the acid) and dry it right away and either paint or cover in oil right away, or I'll get flash rust. As for aluminum, the acid will eat that right away.

I've used oven cleaner (that stuff than comes in an aerosol cans) to clean engines. It eats the grease and leaves it super clean, but will leave the aluminum with a haze, that can be brushed off with a mild wire brush. Of course, not while the engine is in the bike. The oven cleaner will eat the paint on the frame and damage other parts.

Grepper....You are just plain wrong regarding your information about "Muriatic Acid",
as are your recommendations regarding it's proper use and the chemistry involved.

http://hubpages.com/hub/What-is-Muriatic-Acid

Muriatic acid in fact has nothing to do with phosphoric acid diluted or otherwise.

It is dangerous and hazardous to use Muriatic Acid as you suggest... period... and should be completely disavowed! Blue

 

[sgallaty]

7/15

Ambient temperature approximately 95-105 degrees. (and has been every day)

Observed and agitated the solution.

Noticing a finer white foam now instead of the larger bubbles coming from the side with the greater rust deposits.

The solution is becoming somewhat more saturated with particulated ferro phosphates, based on the growing opacity.

The reactions appear to be continuing however my 'feeling' is that the solution is due to be refreshed today based on the color and consistency.

The smell is an issue. The gasses should not be toxic but there are some trace organic compounds interacting here due to my using a hydrocarbon solution (molasses). I do not know what is left over when the molasses dilutes or reacts with the iron or other pollutants on the piece but something in the mixture has an unpleasant odor .. probably from hydrogen combining with free sulfur in the molasses to form hydrogen sulfide.

That said, you want to avoid handling this (or any) chemical solution bare handed. It's also got oils and various other crap in the solution now, definitely not something you want to get into your eyes, mouth or cuts. I feel obligated to say that since I was cavalier about the lack of toxicity. Yes I feel ok putting it on my plants, but I use cow shit for that too and I won't eat that.

 

[grepper]

bluebikerblan: Sorry, I was thinking of hydrochloric. I Agree 100%. It is very dangerous stuff. So is Oven Cleaner for that matter. ALWAYS USE appropriate protection, gloves, rubber smock, and a gas mask in a well ventilated area. Read the bottle and dispose of it properly!
There are lots of articles out there on how to use Muriatic acid to de-rust. If your cautious and use it properly, it can be very effective.

My intent was not to give instructions on how to use it, just stating it can be used and I have done it.

Because it is so dangerous, lately I've been using Vinegar to De-rust.

 

[bluebikerblan]

Thanks grepper there is so very much bad information out there on this subject. It's really easy to get confused. If it was just parts getting ruined....that's one thing but acid dangers and by-products of unsuspected reactions like Chlorine gas are a whole different matter. Blue

 

[sgallaty]

7/15

I replaced the solution, though it looked as if it was really starting to work heavily. I replaced it with twice the previous amount of solution.

I am about to pull the valves and immerse them as well.

 

[kiwi]

Sorry to hijack this thread, but I have a question for Blue or anyone else that may know. How does one dispose of muriatic acid. When I moved into the house I'm in, found a gallon jug hidden in the corner of the garage. Checked with all the authorities on disposal and no one will take it, and if they will, a $100 fee is charged. Got to be an easier and cheaper solution. Any ideas guys. John

 

[bluebikerblan]

Hi Kiwi, Re your question about Muriatric Acid Disposal.... The best route I can think of is to follow a prescribed course of dilution in water, followed by neutralization with Lime. After careful neutralization the reactant products can then be safely disposed of in a variety of ways. As the acid will be converted to a variety of salts in water solution. Here's a good article on the material and safe disposal procedures.

http://www.naturalhandyman.com/iip/infxtra/infmur.html

Do follow all the protective suggestions. keys are well noted in the article.
Please feel free to PM if you're unclear about any of it. Best, Blue

 

[kiwi]

Thanks Blue, good to know. John.

 

[sgallaty]

4 valves just went into the drink.

 

[tonyc]

I saved another Standard tank with four gallons of white vinegar at $2.20 per gallon. Tony C

 

[sgallaty]

7/15
So, today I replaced my solution with twice the volume of fresh solution, and introduced some rusted valves.

I now notice that the new solution does not react to the parts. I am not sure how long the phosphoric acid takes to form or become available, but it appears to be some period of time longer than a few hours.

 

[oldbiker]

hi for cleaning tanks,,, i have used metho,,, at least a couple of litres in the tank,,, it does work,,, but do not leave too long as it gets right in to the seams ,,tiny weene,,, pin holes you don,t even know about ... regards oldbiker

 

[sgallaty]

7/16

having a greater volume of solution seems to be key to sustaining the reaction rate.

agitated container, checked pieces. Heavy rust areas are turning black, some rust has come off the cylinder walls in pieces.

all of the surface rust has been removed, leaving a gentle dark patina that resists flash rust.

 

[sgallaty]

Ok, I think I just stumbled on to something critical.

One of the pieces I was derusting had a heavily oxidized aluminum plate on it. Today when I pulled that out of the bath, the aluminum had been completely deoxidized and was a dull sheen.

That startled me, and I had to think about it for a bit but I believe I understand what's happening, and why.

Here's my theory -

The molasses has phosphor available.

In the presence of hydrogen, which is not normally plentiful, phosphoric acid attempts to form, but to do so it needs 2 more oxygen molecules. It steals these from iron oxide and aluminum oxide.

Furthermore, the stealing of an oxygen molecule from iron oxides releases free iron molecules which when combined with phosphoric acid (H2PO4 / H3PO4 usu.) ends up stealing a loose iron molecule and forming Ferrophosphides (Fe2P / Fe3P) which releases all of the oxygen and hydrogen into the solution (hence the foaming and bubbling). The hydrogen in the solution allows for the creation of more phosphoric acid which starts the cycle over again.

Thus, molasses and water is actually two separate chemical processes in a circuit which both affect the derusting process.

That's my theory anyhow.

To test this theory, I've taken my incredibly oxidized stator and dunked it. I've included pictures for the curious.

 

[sgallaty]

This is a picture for william, because he knows how this part looked before I put it in the solution.

This is without any physical work other than wiping off the slimy muck residue that was adhering to it.

The seal retainer plate (with the three screws) was thick with corrosion.