Vinegar & Citric Acid Rust Removal Questions ?

[mike holden]

Last Year I ran some comparative tests for a SAPFM meeting. Compared electrolysis, citric acid, lemon-lime koolaid, molasses, and evaporust. Upshot was that all worked about the same as far as rust removal. Evaporust was the only one that did NOT etch the metal. YMMV
SAPFM Rust Test.JPG

The rusty auger bits were left overnight in solution. Would a longer bath work better? Would it etch deeper? I dont have an answer for those questions. After this short comparison, I use evaporust as it seems to be fool resistant.
Mike

[glenn bradley]

I realize this is not what the OP asked about but, if he just wants the job done, Evap-o-rust is quick and easy. If he wants to see how vinegar or citrus work, please ignore ;-)

[Dave Anderson NH]

Mike-
I appreciate the fact that you described evaporust as fool "resistant". I have seen clearly demonstrated innumerable times over the years in all kinds of venues that there is no such thing as "fool proof". The fools just keep getting more and more creative.

[Paul Phillis]

I've been exprimenting with both citric acid and electrolysis. Etching has been a concern with citric acid, especially with deeply pitted rust as it is slow to move.

Electrolysis is easy with just a mobile phone charger and a couple of large paper clamps. Use sodium bicarbonate as electrolyte as it is very safe.

Electrolysis has trouble with shifting deep pitted rust. But a short soak in citric acid bath afterwards will then get the rust out of the deeper pits.

[Ray Selinger]

Evaporust is not foolproof. I have a line on a plane when I didn't have deep enough coverage.

[Allan Speers]

I've always wondered what the big deal is with citric acid. Is phosporic acid about the same thing? (White vinegar, too.) They all stop the rust and turn it black, no?

I like phosophoric (spray bottle, or naval jelly) for rusty iron tools like wrenches, holdfsts, and such, because it basically parkerizes them. If you wipe them down and leave them black, they never rust again.

For stuff that I you to want be purdy, you just can't beat electrolysis. - but it has another serious advantage: Electrolysis actually hardens the first very fine layer of rust, next to the good iron / steel. There's a name for this stuff but I forget what it is. Anyway, it can harden it enough that, for instance, you can save a screw or threaded opening that would have been lost with any acid treatment. That' why treasure hunters use it.

[Paul Phillis]

citric acid is different to phosphoric. Phosphoric forms an inert stable iron phosphate compound that sits on the surface of the steel. citric acid dissolves the rust completely leaving only clean steel.

Electrolysis has difficulty cleaning out small holes because electrons tend to go to peaks and avoids valleys. Imagine a cup, the rim would clean up nicely but the bottom remains dirty. It is a reaction between the hydrogen gas and rust that cleans the steel.

[Graham Haydon]

Vinegar has proven to be the the most convenient rust removal method for me. All I need is a plastic tub, some vinegar I can pick up with the weekly shop and a 24 hour soak time.

[Allan Speers]

I've been exprimenting with both citric acid and electrolysis. Etching has been a concern with citric acid, especially with deeply pitted rust as it is slow to move.

Electrolysis is easy with just a mobile phone charger and a couple of large paper clamps. Use sodium bicarbonate as electrolyte as it is very safe.

Electrolysis has trouble with shifting deep pitted rust. But a short soak in citric acid bath afterwards will then get the rust out of the deeper pits.

I have to comment, being a big proponent of electrolysis, on the very common mistake being made here. (VERY common, you are in good company. - So don't feel too bad, Paul!)

First you say "just a mobile phone charger and paper clamps" is good enough, and then you say that the process doesn't do well on deep pits.

OK ...

You see the same thing with guys that are convinced "you can just use an old car battery charger" and then they complain that electrolysis doesn't work as good as they expected.

well, DUH.
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The fact is, you need a VERY GOOD power supply. One that has a quality inverter, so 100% of the current is actually DC. I gurantee that a phone charger is putting out at least 20% ac, which welds the rust right back onto your piece.

You also need enough current, (not available from a trickle-charger) but not TOO MUCH current (such as you'll get form a boost-charger)
And you need current limiting, so you don't get any run-away current due to the low impedance of the mixture. (In other words, no battery chargers (unless modified) and by all means no simple phone charger. (You CAN use a computer power supply, as they are fully regulated, but you're stuck with whatever amperage they put out.)

You also need an absolute minimum of 12v if you want good contact with all of the cathode, but 20V is highly recommended when you have deep pitting, or several pieces bolted together, etc. - And the amperage should ideally be adjusted, based on the size of your piece.

And last, you need a LOT of anode material, with full "line of sight" to the pice being cleaned. "A couple of paper clips" is simply not going to cut it. An entire cage of rebar? Now we're talking. Even better: A bunch of graphite rods or flat graphite plates. Graphite is ideal as it doesn't corrode or get all gummy with deposits.

There are other mistakes commonly made as well, such as the wrong percentage of soda, or not cleaning the anodes, or not having the anodes evenly spaced (which makes the current too low in some spots.) - Or using public water that has traces of chlorine in it.
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Bottom line: Electroylsis is absolutely fantastic, IF you get it set up correctly. This requires time & money, but only once.

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I should also mention that most paper clamps (that I've seen) are made out of stainless steel wire. Using stainless for your anodes is a great way to get cancer. Seriously. look it up.

[Allan Speers]

Last Year I ran some comparative tests for a SAPFM meeting. Compared electrolysis, citric acid, lemon-lime koolaid, molasses, and evaporust. Upshot was that all worked about the same as far as rust removal. Evaporust was the only one that did NOT etch the metal. YMMV

Mike, I don't doubt your results, but I don't understand them, either, since electrolysis (properly done) cannot possibly etch iron or steel. Can you elaborate?

1: What do you mean by "etch?"

2: Did you use a quality, well-regulated power supply? (If not, I'd bet the farm that you were sending a little AC through your tub, which would indeed cause trouble.) Ah, now I see the un-modified battery charger in your pic. There you go. You probably also had run-away current, which causes too violent a reaction. That does 2 things: It damages fine details on your piece (like threads) and it causes the anodes to corrode too fast and get covered in gunk, which then insulates them and lowers the current to below where it can do any good.

(Yes, I've done a lot of research on electrolysis, mostly because MY first attempt was less than satisfying as well.)

[Robert Lang]

Allan, Can you recommend a good, value minded electrical device for electrolysis? Never tried electrolysis but would like to do so using your setup. Thank You!

[Joe A Faulkner]

A low cost battery charger will do the trick.
https://www.youtube.com/watch?v=54ADeB6V1rQ

[Allan Speers]

A low cost battery charger will do the trick.
https://www.youtube.com/watch?v=54ADeB6V1rQ

No, it will not.

It will work, sort of. Then you'll end up posting on forums about how electrolysis doesn't really work as well as you expected.

Been there, done that. Never again. Trust me on this one.

[Allan Speers]

Allan, Can you recommend a good, value minded electrical device for electrolysis? Never tried electrolysis but would like to do so using your setup. Thank You!

I really don't know, Robert. I happen to have a nice lab-grade variable supply, so I use that. You can usually find these used on Ebay, in good condition, for around $100 or so. (Maybe a little more.) If you consider the cost of Evaporust, a good electrolysis set-up isn't actually that expensive. I only recently found out about using more than 12v, and now that I've tried it, I'm a believer, so that's even more reason to get a good power supply.

I've seen articles that show how to modify a battery charger to make it work, though I don't remember all the details. Basically, you add a lightbulb inline, to limit current, and then you add a 12v battery (in series?) so there can be no AC current passed. (I think.)
After all that, you still have only 12v, and non-variable current, which is far from ideal, so I don't see the point.

Also, FWIW, the "treasure hunter" guys claim that the absolute best results are obtained by constantly varying the current (within a safe range) I'm not sure exactly what that achieves.Maybe it turns even ore magnetite into useable, hard metal, I dunno. Power supplies are available that do this, but they cost more.
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I'm about to start refurbing my huge collection of planes & tools, which have been sitting in an unheated garage for over 10 years. It's a huge undertaking and so I've been re-thinking my rust-attack scenario, hence reading this thread. I recently tried Evaporust, and the slightly less-expensive chelation concentrate from Espirit, but the cost is insane, and I really don't see any advantage except maybe for saws with valuable etching. (And chelation won't save badly rusted bolts and threads, as electrolysis can.)

I also looked at Oxyllic acid (widely used by motorcycle repair guys and BMX restorers) and Di-Ammonium Citrate, as mentioned earlier in this thread, but again the cost is just ridiculous. BTW- As best I can tell, Di-Ammonium Citrate is actually the active ingredient in EvapoRust and other chelation products.
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I think that a number of the ideas in this thread have merit, depending upon the specific application. Nothing wrong with good old Naval Jelly (phosphoric acid) in most cases. BTW- If you douse your piece in baking soda & water, after the phosphoric acid, not only does this instantly neutralize the acid, but it causes a lot of the black gunk to sort of "explode" off, requiring a lot less scrubbing at the end.

[Trevor Goodwin]

I just cleaned up a rusty bailey #4 last night using an Australian product, RustBuster, main ingredient is Phosphoric Acid. I wiped a little bit on the sides and sole of the plane and scrubbed away with grey scotch brite type pad, the surface rust came off really easily. I was left with some grey pitting that doesn't bother me - even I could remove I'd still have the cavities. For the non-plated machine screws I've soaked them overnight in the RustBuster. It doesn't etch the steel but converts the rust to a "Phosphorous of Iron" which has a dark grey appearance that is very hard to remove, I don't care though it is protective and the screws aren't visible. Rust on the blade and chip breaker was much harder to remove. I oiled the components after the treatment but I'm not sure if I need to "neutralize" the metal?

I'm calling bullcrap on Allan Speers comments on using battery chargers. I'm an electronics technician and I can tell you that the little amount AC ripple that passes through a charger is of no concern, and putting a battery in series will not eliminate it. Phone chargers do not generally have "20% AC", especially modern ones that are based around the 5V USB standard. Unless you have 50 gallon tub for your electrolyte with the anode-cathode separated too far, 12V battery is sufficient. A car charger is naturally current limited but you might want to restrict the current further to reduce resistive and chemical heating effects; a car interior light-bulb could be used for your current limit so could a resistor. Note that some (expensive) car chargers have fancy battery monitoring electronics that prevent you from using them for this purpose. An old computer power supply would work fine and they usually have their 12V current rating on the label.