# Cleaning Rusty Old Collets



## Halfnuts (Nov 26, 2013)

I picked up an old Speedchuck made by Hardinge/Sjogren with a set of collets off of eBay.  The collets were covered with sawdust and were a little rusty.  I thought I'd strip the rust off of one and see how well it will clean up.  So I filled a water glass with warm water and added about a tablespoon of Crystal Drain Cleaner from Home Depot (mostly lye) and stirred.  




After about an hour the solution turned dark and I thought I'd take a look.  Took the collet out of the solution and washed with hot water and detergent, then rinsed in hot water, toweled dry and coated with WD40.  Result was better than expected.  Rust and dirt disappeared.


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## Dave Smith (Nov 26, 2013)

They will look nice when you finish them all---good job !!!---Dave


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## RandyM (Nov 26, 2013)

GREAT score! Isn't it fun to save things that others would throw away? You'll have a nice set once all cleaned up. Thanks for the post.


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## Halfnuts (Nov 26, 2013)

Ok, since y'all asked, I decided I'd put a phosphate coating on the collets.  

First I cleaned them by sonicating in a hot solution of a caustic detergent (Micron 90) to remove surface oils and grime.    Dishwashing detergent would be a good substitute.  

Then rinsed with hot water and put them in a bath of 5% phosphoric acid made with hot water.  I usually do only a beaker-full at a time, so don't measure very  carefully.  This time the quantities were large enough I could measure  them easily.





While they were bubbling away in the fume hood (at work), I experimented and found that 0.5% phosphoric acid would have worked fine, too.  The gas bubbling up from the surface is hydrogen, the result of the conversion of Iron (III) oxide to Iron phosphate.   Because of the risk of ignition and the acrid smell of the acid, this step is best accomplished in a fume hood.




After about an hour the solution began to turn dark, indicating that the surface rust had been converted to iron phosphate and had been dislodged.  There is nothing to be gained by leaving the work in the acid bath any longer.  I removed the collets from the phosphoric acid solution and rinsed them in hot water and brushed off a minor amount of loose iron phosphate that remained from the surface rust.  Then I toweled them dry and sprayed with WD-40 and put them in a 70C (158F for those of you in Iraq and the U.S., the only two countries still using the Imperial system of measurement) oven for about an hour to dry any remaining water.




Result was a fairly even layer of black iron phosphate which, while not an especially durable coating, will nevertheless protect the collets from rust for some time.  There are other coatings that can be applied to steel, but if you want to remove surface rust, it's hard to beat phosphoric acid, because besides removing surface rust it leaves behind a rust resistant finish.  


In the process, there are two reactions taking place.  The first occurs at the site of surface rust which is iron oxide.  The phosphoric acid reduces the iron oxide to iron phosphate with the creation of water.  No gasses evolve. 

At bare iron surfaces, the iron is converted to iron phosphate by the action of phosphoric acid.  When the phosphate from the acid jumps ship and combines with the surface iron, the remaining hydrogen atoms combine creating hydrogen gas which can be seen as bubbles forming at the bare metal surfaces.  At first you won't see many bubbles, and it looks like not much is happening.  But with time, more bubbles will form and when the rust is completely converted to iron phosphate, the bath will begin to bubble more vigorously.  

The usual caveats apply.  I wore gloves, eye protection, a lab coat and worked with the acid in a fume hood in a commercial chemistry laboratory.


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## xalky (Nov 26, 2013)

Nice job. I have quite a few old things around here that could use this treatment. 

I read somewhere that theres a concrete etching acid that is primarily phosphoric acid. I believe Home depot sells it in the masonry section. Anybody know what I'm talking about?


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## Halfnuts (Nov 26, 2013)

Yes, it's supposed to contain phosphoric acid.  If it does, you're there.  Was there yesterday and looked at a label on a jug of it, but without my glasses, in the dim light I couldn't read the tiny print.  

One of these days EPA is going to outlaw phosphoric acid for that use because runoff containing phosphoric acid adds the one nutrient that freshwater systems need to spark algae blooms:  phosphate.   It's likely there is already a replacement for it which probably contains citric acid, EDTA and a mild detergent of some sort.


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## MikeWi (Nov 26, 2013)

xalky said:


> I read somewhere that theres a concrete etching acid that is primarily phosphoric acid. I believe Home depot sells it in the masonry section. Anybody know what I'm talking about?



It's been a very long time, but I used to sell concrete etchant that was muriatic acid, a mix of water and hydrochloric acid.  I did a quick search and it is used to clean metal too, but I didn't see what concentration is used.

edit:
(For the non-chemists here) I took the advice I found on this forum and used Evapo-Rust on my old grinder.  That stuff really is amazing, and according to the label is completely safe to use.  :thumbsup:


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## itsme_Bernie (Nov 26, 2013)

Is this close to "Parkerizing" ?


Bernie


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## xalky (Nov 26, 2013)

MikeWi said:


> It's been a very long time, but I used to sell concrete etchant that was muriatic acid, a mix of water and hydrochloric acid.  I did a quick search and it is used to clean metal too, but I didn't see what concentration is used.
> 
> edit:
> (For the non-chemists here) I took the advice I found on this forum and used Evapo-Rust on my old grinder.  That stuff really is amazing, and according to the label is completely safe to use.  :thumbsup:



I have muriatic acid here and I also have Sulfuric acid (drain cleaner). Muriatic acid is hard to nutralize and I've read that it embrittles steel. It works great to get rid of the rust though. The awesome part about the Phosphoric acid is that it actually converts the rust to iron phoshate which essentially ends the reaction, and adds a nice protective coating to boot. )


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## Halfnuts (Nov 26, 2013)

The problem with muriatic acid (hydrochloric acid is same thing) is that the acid is completely dissociated.  Hydrogen ion, or actually the hydronium ion (H3O+) is completely separated from the chloride ion.  That means that when you're done with whatever etching or cleaning you're doing, you need to get rid of the hydrogen and chloride.  You can easily find things that will suck up hydrogen ions; baking soda (sodium bicarbonate) is a good neutralizer, but the remaining chloride is a real bugger.  All chlorides are soluble.  Nothing will bind it.  And so the chloride, if it gets deep down in a crevice in your iron casting, or in a weld, sits there, and being highly electronegative, it remains very reactive.   And despite your best efforts, it will continue to rust.  After using HCl to de-rust metal some folks recommend heating the part to 350F or equivalent to drive the chloride out of the pores in the metal as chlorine gas.   But then you run the risk of warping a machined part or ruining the temper of the metal.  

For that reason, weak acids like oxalic acid, citric acid, or phosphoric acid are preferred.  I've had good luck with 1% citric acid in water.  It's relatively safe and not very toxic (used in food additives) and should be available off of eBay.   You can also strip rust by treating the metal with hot lye (sodium hydroxide), the primary component of most drain cleaners.  But as soon as the metal is washed free of the lye solution, it will immediately form a thin layer of surface rust, so must be coated with WD-40 or way oil.  

Don't get me started.  I do this all day.

- - - Updated - - -



itsme_Bernie said:


> Is this close to "Parkerizing" ?
> 
> 
> Bernie



Bernie,

You have a good eye.  Probably two of them.  Yes, phosphating is similar to Parkerizing.  Look it up on Wikipedia; they have a good description there.  A gunsmith friend is an encyclopedia on metal coatings.  It's amazing what you can do with steel.


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## Halfnuts (Nov 26, 2013)

xalky said:


> I have muriatic acid here and I also have Sulfuric acid (drain cleaner). Muriatic acid is hard to nutralize and I've read that it embrittles steel. It works great to get rid of the rust though. The awesome part about the Phosphoric acid is that it actually converts the rust to iron phoshate which essentially ends the reaction, and adds a nice protective coating to boot. )



Marcel, at the risk of sounding like a know-it-all (which my kids assure me, I'm not!) a couple minor points.  Sulfuric acid is battery acid.  You don't want to dump that down the drain or you could destroy your plumbing.  I think you meant to name another chemical that starts with an "S" sodium hydroxide (lye).  That's the stuff that's used for drain cleaner because it reacts with cooking grease and most anything organic (even your skin) and turns it into a slippery soapy material that flushes down the drain easily.  

The reaction with phosphoric acid proceeds simultaneously in two directions.  One, reduces red iron III oxide to black Iron II oxide (magnetite, same as iron ore), which falls to the bottom of the container.  Once all the rust has been reduced (destroyed), you're correct that the reaction between iron oxide and phosphoric acid ceases.  However all along there has been another reaction taking place.  The reaction between the iron in the part to be cleaned and phosphoric acid continues as long as there is acid and iron.  Eventually, the buildup of iron phosphate should block any further effect of the acid on the base metal, but I've never waited long enough to see that happen, and I've never wanted to risk the possibility of hydrogen embrittlement.  They say that's a possibility.  I don't know anyone who knows for sure, but I think it's best to stop when the rust is gone and the part is coated with black iron phosphate.


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## xalky (Nov 27, 2013)

http://www.doitbest.com/Chemical+dr...cts+Inc-model-LF-P-24-doitbest-sku-462234.dib I assure you this stuff is at least 98% sulfuric acid. Backyard chemists use it all the time. Including myself. I''m a backyard chemist. Sometimes you just can't buy the real deal so you make due with whats commercially available. This stuff will destroy metal pipes. I don't use it for that but I have in the past to  clear out old cast iron pipes that clogged up with rust scale inside. It's perfectly safe for plastic pipe.

Not all drain cleaners are the same, some are lye based as you said, and some are enzyme based.


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## Halfnuts (Nov 27, 2013)

I learn something new every day.  First time I've ever heard of sulfuric acid for drain cleaner.  It seems it would be hard on thin metal pipes like sink trap and tailpiece, and the microbes in the septic probably wouldn't like it either; not that they'd like lye-based drain cleaner!


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## MikeWi (Nov 27, 2013)

Halfnuts said:


> I learn something new every day.  First time I've ever heard of sulfuric acid for drain cleaner.  It seems it would be hard on thin metal pipes like sink trap and tailpiece, and the microbes in the septic probably wouldn't like it either; not that they'd like lye-based drain cleaner!


I sold all that stuff at a home center 30 years ago.  One customer did have the sulfuric acid based cleaner go right through his P-trap, another using Lye some how let it recrystalize in the drain blocking it solid.  How the heck that could happen I don't know, but that's what he claimed anyway.  I remember another one told me he used Lye once and had to call the fire dept! LOL  he refused to explain further, but you could see him getting angry just thinking abouit it LOL


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## Armor (Nov 29, 2013)

Trisodium phospahte .

As used in a park finsh  check Brownell's in Iowa for gun bluing and stuff.

Jeff)


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## Wheels17 (Nov 29, 2013)

Before you go too far, I'd treat one with Evaporust and see what you think.  Most of the techniques I saw when  I scanned the comments have a risk of attacking the good metal as well as the rust.  Evaporust works by a different principle, and won't attack the metallic iron. I've treated a lot of rusted items with it and have been very happy with the results.  I've even cleaned up milling cutters without damage to the cutting edges (which were not rusty).

That said, the iron phosphate coating came out very nice.


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## Halfnuts (Dec 1, 2013)

I'll look for it but I've never seen it on the shelf.  I have a copy of Angier's Firearm Bluing and Browning.  Some of the techniques described would work on machine tools that sit for too long on a shelf.


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## Bill Gruby (Dec 1, 2013)

Evaporust should be readily available in Ca. even with your strict green laws. It can be put down the drain. Harbor Freight will have it.

 "Billy G"


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## Halfnuts (Dec 1, 2013)

Bill Gruby said:


> Evaporust should be readily available in Ca. even with your strict green laws. It can be put down the drain. Harbor Freight will have it.
> 
> "Billy G"



I'll look for it next time I go to HF.


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