Cleaning rust with caustic soda

[Argentino]

Howdy,

I´m trying to define if this might be a good and simple method for rust removal.

I´ve recently acquired an old RRB (Argentine contract in .43 Spanish). Both the internals and bore are pretty decent however the external look is far from nice, all covered in rust.

I´ve attempted to remove it with some oil and a bronce brush but I´m not satisfied with the results so far.

So, my question is: did anyone try with caustic soda?

From what I´ve heard it seems to be a good way of getting rid of rust (or maybe neutralizing it?) plus it doesn´t harm the blueing.

Anyway, I would feel safer if I get some first hand experiences with it before trying.

I already know about the safety precautions about this stuff, and also know of some other methods that might be even better (such as an electrolytic tank) however I would like to learn about this specific method please (caustic soda + water solution)

Any thoughts/recommendations?

Thanks,

Argie

[gnostic]

Citric acid, Leme-Shine or Navy Jelly will remove rust...

[TCLouis]

Naval Jelly will take the bluing with the rust as I remember it.
It does remove rust very well though.

[rwadley]

Ballistol on a rag works on light rust. Alternate with bronze wool.

[John Boy]

50:50 mix of acetone & ATF

[pietro]

I´m trying to define if this might be a good and simple method for rust removal.

So, my question is: did anyone try with caustic soda?

I would like to learn about this specific method please (caustic soda + water solution)

Any thoughts/recommendations?





Nope - Since I don't care to mess with dangerous chemicals, I never bothered to try a caustic acid.

I am completely satisfied with the rust removal results, I obtained, from using BIG 45 FRONTIER metal cleaner, dipped in oil.

http://www.big45.com/

IME, although the scrub pad looks rough enough to scratch metal, it in fact removes rust only, every time, w/o effecting any bluing.


.

[Der Gebirgsjager]

Actually, caustic soda is what most bluing salts are made of. If you put a rusty gun in a bluing tank it will come out blue except where the rust is, and that will still be rusty. What I suggest you do is invest in some of Brownell's Rust Remover. Works great, eats all the rust off including in the pits and won't harm the steel.

[fiberoptik]

Actually, caustic soda is what most bluing salts are made of. If you put a rusty gun in a bluing tank it will come out blue except where the rust is, and that will still be rusty. What I suggest you do is invest in some of Brownell's Rust Remover. Works great, eats all the rust off including in the pits and won't harm the steel.

Isn't it just muriatic acid?


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[500MAG]

I like Birchwood Casey blue & rust remover but like the product says it removes the blue too.

[fast ronnie]

Muratic acid will take off the rust, BUT it is about the fastest way there is to take off all the bluing. Wipe on, wipe off, bluing gone. Yes, it will take off rust, but do you want to re-blue? Evaporust will take off rust, but don't know if it will affect bluing. I have some, plus an old barrel. It would be interesting to find out. Right now I have a mold in Evaporust to get rid of some surface rust. It does not affect the steel, but it does real good on the rust. Water soluble and not harmful to the environment. Just put on some rust preventative after rinsing off with water.


Isn't it just muriatic acid?


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[Der Gebirgsjager]

Isn't it just muriatic acid?


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That I do not know. They actually have two products, "Brownells Rust Release" and "Brownells Rust and Blue Remover" item numbers
#082-000-013AN and #082-054-032AN respectively. I have used the last one, but not the first. I do not know what the composition of the liquids are, but the one I have used does a great job. The difference is that the first is used straight out of the one gallon bottle and the second is a concentrate that mixes 1:1 with water (1 qt. concentrate makes 2 qt.s remover).

[oldred]

Caustic Soda is useless for removing rust and ANY chemical that will remove rust will also remove bluing! Bluing is also an oxidation process and is actually just another form of rust so about the only options are to remove the rust with light abrasion, such as rubbing with OOOO steel wool, or just acid strip the rust and bluing then re-blue. ATF and steel wool, or about any oil, will work quite well but depending on the extent of the rust the blue is apt to abrade away before the rust is completely gone. Any good gun oil, machine oil, motor oil, etc will work as a lubricant for the steel wool and the film oil left will inhibit further rusting by sealing off the oxidized area from oxygen and moisture, gun oils or any other oil with corrosion inhibiting additives are the best choices. No oil will actually help remove rust but it does provide a lubricant for the steel wool and does a lot to prevent abrading the bluing itself, never rub a blued surface with dry steel wool!


Also Muriatic acid is a terrible choice for removing rust from steel, it certainly will remove the rust in short order BUT it then starts a chemical reaction on the surface of the metal that is very difficult to completely stop, basically it induces further rusting! The correct acid for doing this is phosphoric acid which removes the rust but also, just like any other acid, will remove the bluing. When phosphoric acid is used it stops the rusting process and leaves a thin phosphate surface that is not only oxidation resistant but will neutralize any rust remaining in tiny pits on the surface. About the only real option to remove rust while leaving the bluing, or at least as much as possible, is rubbing with steel or bronze wool and oil, personally I have had much better luck with steel rather than bronze wool.

[Ballistics in Scotland]

Oldred is right that any chemical rust remover will be a bluing remover, and caustic soda is quite ineffective. Muriatic acid is simply another name for hydrochloric acid, and by no means useless for the purpose if dilute. I don't think it is at all likely to actually erode the steel, but it may be that the tendency to after-rusting owes something to leaving the pore structure of the metal open. There is a good chance that cleaning carefully with boiling water, bluing before it is cool enough and then oiling will prevent any problem.

A much better rust remover is phosphoric acid, which simply is naval jelly, although if you buy phosphoric as the common 85% solution (which is likely to be cheaper) it will be a bit more pourable. It will still leave a satin texture, which looks good when blued, and any remaining pits will look much less conspicuous than any physical cleaner can make them. I wouldn't want to use any chemical rust remover on a rusty bore, but although I vaguely remember seeing some pretty reputable authority recommending hydrochloric as a desperate measure, I would much prefer phosphoric if I had to.

You should beware of more complex rust removers which offer to prevent future rusting. They mostly contain phosphoric acids and also iron, zinc or manganese phosphates, which leave a dark protective coating not unlike a rather thin version of phosphating. I doubt if it is anything like as good as real phosphating, and if you plan to blue afterwards, it isn't as good as nothing. There are at least two different phosphates of iron, and I don't know which is the passivating one, but the reaction with pure phosphoric acid produces ferric phosphate, so I wouldn't reuse a bath of the stuff on metal which is to be blued.

[nicholst55]

Muratic acid will take off the rust, BUT it is about the fastest way there is to take off all the bluing. Wipe on, wipe off, bluing gone. Yes, it will take off rust, but do you want to re-blue? Evaporust will take off rust, but don't know if it will affect bluing. I have some, plus an old barrel. It would be interesting to find out. Right now I have a mold in Evaporust to get rid of some surface rust. It does not affect the steel, but it does real good on the rust. Water soluble and not harmful to the environment. Just put on some rust preventative after rinsing off with water.

Evapo-Rust will remove the bluing if the part(s) are soaked long enough. It states that on the label and I can verify that it's true.

[fiberoptik]

Used muriatic acid to clean urinals with green scrubbies & bare hands in the Corps. Really hard on skin!


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[castalott]

If I Remember Correctly

Muriatic acid ( Hydrochloric acid or HCL) is an acid and a 1 on the PH scale. Water is 6 or 7 depending and is considered neutral. Caustic soda is 14 on the PH scale and is considered a base which for our purposes is the opposite of an acid. Ph measures varying degrees of everything to show strength or dilution. The closer you get to 1 or 14, the more dangerous it is.

Bases normally remove greases and oils or organics. Then acids are used to remove rust and corrosion.

When I acidized boilers for a living ( That 600 foot building you see at power stations is built around a 600 foot boiler) , you always started with a base to remove any organics or 'greases'. Some of those can be amazingly resistant to acids. Then you used acid to remove corrosion. Most of the time HCl was used with an inhibiter so an acid would attack corrosion but not 'virgin' metal. This inhibitor looks like spaghetti under a microscope and the ends stick to pure metal but not rust and corrosion. The acid can't get to pure metal but is free to attack rust.

HCL at 110 F is a wonderful thing. HCl at 200 F is a monster that will dissolve anything you are trying to save. Temperature is critical as is the inhibitor.

Now for the warnings... You don't want anything at either end of the ph scale on you or breathed in. HCl ( 15%?...not 28%)is , to me, A milder acid. The stronger acids will burn you in short order. Caustic Soda will burn you BAD in very short order with the correct amount of water/heat with it.

Citric acid is fairly mild but is still an effective acid.. just takes longer. Baking soda ( Sodium bicarbonate) is a fairly mild base and just takes more time and volume. Read up before using this stuff as my memory may be corrupted..

Now a short story...

Years ago we were neutralizing 1000 gallons of sulfuric acid with caustic soda. We were circulating the sulfuric acid in and out of a 2000 gallon tank on a tractor trailer made for such a thing. we injected the caustic soda into the stream to mix at a slow rate and the 2 opposite ends pf PH would cancel each other out.....

Confusion abounded that day and somehow a full stream of caustic soda was injected into the 1000 gallons of sulfuric. Luckily the tank was thick and withstood what happened next. '

I swear the tractor trailer started bouncing up and down....leaving the ground. The top hatch wasn't locked down and a tornado of black, ugly liquid shot up probably 50 or more feet. The other guys with me didn't understand what we were looking at.. they just stood there in awe. I yelled "RUN!!!!" Luckily we ran away from where all this came down. We washed everything with fire hoses ( It was in a plant and everything drained to a hazard pit- not a city drain.) but the buildings lost their paint. The trucks had chemical resistant paint on them but they were no longer red and gray but pink and charcoal colored. Be careful with these chemicals... Your eyes and lungs are not replaceable...

[Frank46]

Sounds like Halliburton trucks. We had a waste water treatment plant and two 13 million gallon storage pits that were cenverted from old gas holders. Unfortunately some genius decided that the lines from the plant were to be made from fiberglass and were glued together. temps had to be held at 165 degrees or the glue would soften and melt. To get the temps down they were supposed to inject water to cool it down. Chart recorder showed 200 degrees and glue melted and blew off two drain valves. Made for interesting traffic direction. Frank

[Ballistics in Scotland]

Those alarming stories are entirely valid. But we do have hydrochloric/muriatic acid close to us, right where nature has cunningly arranged to minimize motion sickness by placing our centre of mass. For it is the main stomach acid, at a Ph from 3.5 to 1.5, which is a lot. The stomach lining resists it extremely well, although painful reflux occurs if relaxation of the sphincter at the bottom of the oesophagus permits it to gurgle up to more sensitive tissues.

I have somewhere an account of a scientist in the 1930s dosing himself experimentally with enough to raise the normal level very considerably. It did him no harm to speak of, but if he had been subject to reflux, he would have wished he wasn't.

The degree of dilution is everything. I'm told that the British army resisted the potato-peeling machine because a little suffering was conducive to good order and military discipline, and the same may apply to the US Marines and hydrochloric acid. Rubber gloves would be advisable, but properly diluted there should be no actual danger of serious harm with latrines or rust removal. I recently did some rather finicky concrete work, getting the stuff between the brickwork and a steel security door for my workshop. We think of mortar as being only mildly alkaline, but I had a rather tender feeling in my hands for several days.

That is a good point about temperature, and any reaction which involves the meeting of an acid and an alkali evolves heat, above boiling point when they are strong. Indeed so does the meeting of a strong acid with water, for which reason it is important to add acid slowly to the water to avoid violent splashing, rather than water to acid.

Even etching metal evolves heat. It shouldn't be a problem with dilute hydrochloric and steel, but when actual etching is required, it is important to keep up a considerable volume, relative to the area to be etched. Here is some of my handiwork of the 1980s, done with enamel paint, Letraset transfer lettering and 15% nitric acid, which does a lot other acids won't. The paint was pretty secure, but I found that if I hung it in a shaped vessel to minimize the amount of acid required, the heat would lift parts of the Letraset. With more acid to warm up less, this didn't happen.

170382

[MediumCore358]

Caustic soda is is sodium hydroxide, continued use will create rust. In grease manufacturing we diluted it with water in 55 gal drums and once the heat from reaction dissipated it was added to the kettle for soap base.

[MediumCore358]

Sodium hydroxide isn't an acid it's alkaline with a ph of 14

[sandman228]

sodium hydroxide is some nasty stuff . I know from experience what it will do to flesh if you get it on you . ive neutralized and cleaned rail tank cars that have hauled it .

[Ballistics in Scotland]

Yes indeed, and it will eat through a lot of clothing, gloves etc. which will protect you from acids.

[williamwaco]

I use CLR on molds and tools and occasionally on gun parts but if you use it on guns it WILL remove bluing.

It works very quickly and easily with no damage to the underlying metal.

[Argentino]

Thanks for all the info guys.

Unfortunately, most of suggested products are not available at my country. But no worries I´ll try to find another substitutes.

I forgot to mention another option I would be tempted to use: white vinegar.

I did try it on barrel bands and after a couple hours they came out pretty clean and rust-free;
very good results except for a dull grayish color on metal, but rust was completely gone (besides, I´d always prefer a dull gray finish rather than shiny metal).

I´m now thinking of using this same stuff (50% white vingar +50% water) on barrel (just the outside surface, not the bore).

Thanks again,
Argie.

[fiberoptik]

Vinegar left too long removes chrome from old tools, I found out.


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