Rusty tools and muriatic acid

[gf0012-aust]

I realise that this has prob been done to death...
I recently bought a batch of tools and drill bits which I have now found out that the prev owner had soaked, cleaned in hydrochloric acid

I've had them in an electrolysis bath for the last 3 days in the hope that it will neutralise the oxy reaction - the rust is all gone and some are still black, whereas a few are dull grey machine finish. the bits are all HSS and decent quality othewise I wouldn't bother

question is that Ive also read that you can also netralise the reaction by immersing them in a paste of bicarb soda and water

are there any engineers, machinists and chemists on here who have done this?

am int'd in the actual ratios and duration of immersion etc...

once rust is gone is wd40 sufficient to use as a film?

 

[pizza]

as someone with an engineering and chemistry background...

HCl solution is actually a gas dissolved in water, and it should evaporate cleanly with no residue. in theory, it should be long gone.

i'm not sure i understand the tool history though.

so they were presumably rusty, and some guy put them in HCl solution to remove the rust? and then he did who knows what with them, possibly didn't oil them, they got rusty, and you received them in rusty condition?

so now they're in an electrolysis bath to remove the rust? what is the bath solution? table salt (NaCl)?

I've had them in an electrolysis bath for the last 3 days in the hope that it will neutralise the oxy reaction

what do you mean by oxy reaction?

just get them cleaned up, give them a scrub if necessary, and then thoroughly clean them in lots of clean tap water.
immediately dry them (perhaps with heat) and apply a light oil before flash rust can occur. i like food grade mineral oil from the pharmacy, but everyone's got their own favorite thing: https://www.garagejournal.com/forum/showthread.php?t=437061

 

[gf0012-aust]

ack on your summary of the tool history ....

and yes, oxy reaction = flash rust

the electrolysis bath is about 50 litres water and a cup of sodium carbonate

I'm using a drum brake as an anode and its hooked up to a DC inverter mig welder running at 20amps (lowest setting)

its certainly effective at getting rid of the rust, I just want to make sure I can keep it off now

I was going to warm them up with the LPG/propane torch anyway, I just want to make sure I only need to do this once!

ta for the assist

 

[Ole Slewfoot]

If you want be super proactive, remove from bath, scrub in clean(and maybe a little soapy) water(keep wet, keeps the stuff from sticking as much) then straight to acetone bath to **** the water out. Heat and gas both lead to flash rust.
Real world,scrub a bit in hot water, then in wd-40, and they will be fine

 

[gf0012-aust]

If you want be super proactive, remove from bath, scrub in clean(and maybe a little soapy) water(keep wet, keeps the stuff from sticking as much) then straight to acetone bath to **** the water out. Heat and gas both lead to flash rust.
Real world,scrub a bit in hot water, then in wd-40, and they will be fine

Does wd40 get “gummy”?

 

[pizza]

the acetone thing is good advice. using alcohol instead would also work, but it doesn't evaporate as quickly as acetone. the point is that both are miscible with water (and so will dilute the water residue to almost nothing) and also evaporate more quickly than water.

i've never tried using wd40 like that, but it's not my first choice for lubrication or protection. most of it evaporates away. but if it has corrosion inhibitors in it, maybe that's fine. (i don't know if it does)

 

[Ole Slewfoot]

Wipe it with a WD rag, and it dries to a thin (microns) film, unless the metal is really porous...then leave it thicker. It's probably not the best, but works fine where condensation does not form standing water on the tools.

 

[B.S.A. (ret.)]

I have cleaned up many a rusty tool using a bath of straight white vinegar (available at any grocery store), followed by a rinse in t hot tap water. Remove from hot water, dry with a heat gun and then coat and rub with WD-40 to remove loose black residue and keep from further oxidation. Tools will be grayish black from then on but will work just fine.

 

[tym]

Wipe it with a WD rag, and it dries to a thin (microns) film, unless the metal is really porous...then leave it thicker. It's probably not the best, but works fine where condensation does not form standing water on the tools.

I've also used Sili-Kroil, as it leaves a silicone coating behind that is not sticky or tacky.

 

[driftpin]

Six-percent vinegar, called 'cleaning vinegar' instead of weaker 'food-grade' vinegar. Before/after.

When my neighbor got these, after cleaning-out a shed for someone, he hadn't even-bothered to drain the water they were sitting-in. I left 'em in the 6% vinegar solution for maybe 3 days. I could have wire-brushed them to remove more but the cadmium plating on some was peeling, that's a known carcinogen.

Home Depot carries a 30% vinegar, be-careful what you put-into that.

 

[gf0012-aust]

Worth a read....

https://www.practicalmachinist.com/...d-history/rusty-drill-bits-147681/index2.html

 

[RTM]

Yeah, Muriatic acid is a *****. On another forum, guy had a bottle under his work bench, and a few years later, discovered an entire toolbox had rusted through, and the tools inside destroyed.

Can’t find the details, so take this as a potential raving from someone whose memory is better than his search skill at the moment.

 

[Warpaint12]

Done that myself. Works great. Just not for show tools. LOL

 

[Vvmvbb]

as someone with an engineering and chemistry background...

HCl solution is actually a gas dissolved in water, and it should evaporate cleanly with no residue. in theory, it should be long gone.

—-snip

I think you might be thinking of chlorine gas (Cl2) or maybe hydrogen gas (H2)? HCl refers the ions H+ and CL-, not the gases

 

[pizza]

I think you might be thinking of chlorine gas (Cl2) or maybe hydrogen gas (H2)? HCl refers the ions H+ and CL-, not the gases

?

first of all, chlorine's chemical symbol is Cl, not CL.

"HCl" as-written actually does not refer to any particular state of matter. without context, you can assume the pure state at STP.

HCl -- or hydrogen chloride -- is a pretty volatile substance. it boils at -85°C. at STP, HCl exists as a gas (written "HCl(g)").

when this hydrogen chloride gas is dissolved in water, it can be referred to as hydrochloric acid or as a solution of HCl. it can be written as "HCl(aq)" which is a convenience term for "H+(aq) + Cl-(aq)" (or more accurately "H3O+(aq) + Cl-(aq)").

but because of its high vapor pressure, HCl(aq) will fume appreciable amounts of hydrogen chloride gas/mist. this is why an open bottle (or a loose cap) will ruin nearby equipment and also presents an inhalation hazard. it's very corrosive.

 

[PCMusicGuy]

I know it doesn't answer your question, but if you haven't tried Evaporust yet you are doing yourself a disservice. I had been doing the electrolysis route but for small stuff, I won't be doing that anymore.

 

[barnonline]

Quote from the link gf0012-aust provided:


Howd,

Ah, no, as respectfully as I possibly can, I must warn you against using Muriatic Acid (Hydrochloric Acid) on steel. Yes, it takes the exisiting rust right off. BUT, and it is a BIG BUT, it results in the steel rusting forever.

The culprit is that chloride ions chemically combine with the steel and start a "bucket brigade" reaction where they capture an Fe and then, in the presence of atmospeheric moisture and oxygen, give the Fe up to oxygen. The Cl ion then grabs another Fe, and the process repeats.

This is what causes "pitting". Sometimes the pits look like worms or termites ate the steel. Each pit is the site of one or more chloride ioins burrowing into the steel.

This is why road salt rust on your car is difficult to stop once started.

The only way to stop it is to remove the chloride ion by abrasive methods or by electrolysis. You cannot wash the chloride ions off, they are chemically combined with the steel.

Phosphoric Acid is also available economically at your local hardware store as a Concrete Rust Stain Remover. Any such product will have an MSDS sheet which will identify the acid used; pick a product with Phosphoric Acid.

If I had to make a second choice, it'd be H2SO4.

If you don;t believe this, safely pour yourself a small glass jar of Muriatic and a small glass jar of Phosphoric and drop a wad of clean steel wool in each. Do this outdoors and keep them away from eachother so there is no question about fumes.

This is also why bleach is bad news to steel.

John R.

 

[pizza]

The only way to stop it is to remove the chloride ion by abrasive methods or by electrolysis. You cannot wash the chloride ions off, they are chemically combined with the steel.

i read that too, but iron chlorides are pretty soluble in water, so i'm skeptical of that statement.

granted, it might need a scrubbing, but you should be able to remove it with water.

 

[OneDollarSaab]

Time for an experiment, I've got some old pool acid and harbor freight wrenches that are collecting dust.

 

[gf0012-aust]

I know it doesn't answer your question, but if you haven't tried Evaporust yet you are doing yourself a disservice. I had been doing the electrolysis route but for small stuff, I won't be doing that anymore.

evaporust isn't available here

 

[Ole Slewfoot]

https://evapo-rust.com.au/Shop.html ...you can even get it without all the extra water they make us pay for. AKA concentrate.

 

[gf0012-aust]

https://evapo-rust.com.au/Shop.html ...you can even get it without all the extra water they make us pay for. AKA concentrate.

ack

ah my google-fu is weak. everytime I asked at various places I was told we couldn't get it

will come in handy as I jiust picked up a 3ft blacksmith vice. my longest plastic tub was 2" too short for a full immersion an electrolysis job (undismembered!)

 

[Vvmvbb]

?

first of all, chlorine's chemical symbol is Cl, not CL.

"HCl" as-written actually does not refer to any particular state of matter. without context, you can assume the pure state at STP.

HCl -- or hydrogen chloride -- is a pretty volatile substance. it boils at -85°C. at STP, HCl exists as a gas (written "HCl(g)").

when this hydrogen chloride gas is dissolved in water, it can be referred to as hydrochloric acid or as a solution of HCl. it can be written as "HCl(aq)" which is a convenience term for "H+(aq) + Cl-(aq)" (or more accurately "H3O+(aq) + Cl-(aq)").

but because of its high vapor pressure, HCl(aq) will fume appreciable amounts of hydrogen chloride gas/mist. this is why an open bottle (or a loose cap) will ruin nearby equipment and also presents an inhalation hazard. it's very corrosive.

Yeah, I know. So you were referring HCl gas. As discussed, bound ions don’t evaporate and won’t be long gone as you suggested.

 

[pizza]

I've had them in an electrolysis bath for the last 3 days in the hope that it will neutralise the oxy reaction - the rust is all gone and some are still black, whereas a few are dull grey machine finish. the bits are all HSS and decent quality othewise I wouldn't bother

question is that Ive also read that you can also netralise the reaction by immersing them in a paste of bicarb soda and water

As discussed, bound ions don’t evaporate and won’t be long gone as you suggested.

the OP suggested that neutralization with a base might be necessary. i was saying that it's not since the excess HCl is long gone. the dissociation reaction is reversible, and the excess fumes off (unlike many other acids like H2SO4). the remaining residue would be no worse than table salt.

but of course you have to remove any salts present (FeCl2, FeCl3, ...) with plenty of water and scrubbing.

get them cleaned up, give them a scrub if necessary, and then thoroughly clean them in lots of clean tap water.

what exactly the original owner of the tools did after treating them with HCl(aq) and before giving them to OP is not clear though.

something not clear to me is if -- despite iron chloride's high solubility in water -- chloride ions can really hide in pitting. is thorough cleaning in water not good enough like that guy on the other forum said? maybe that's true in the situation of a rusty car where the material's like swiss cheese, but what about after a quick dunk in HCl(aq) to treat surface rust? i don't really know.

 

[thool]

ack

ah my google-fu is weak. everytime I asked at various places I was told we couldn't get it

will come in handy as I jiust picked up a 3ft blacksmith vice. my longest plastic tub was 2" too short for a full immersion an electrolysis job (undismembered!)

You might like Evapo-Rust. I've seen people use it on entire engine blocks by bagging the block, immersing the bag in a barrel with the top of the bag exposed, filling the barrel with water to press the bag against the block, and then dumping Evapo-Rust in the bag.

I've used it on rusty tools, clean up with a brass brush, and another soak.