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topic 12044

Asking for formula for hydrochloric acid to strip motorcycle parts


(a fun & ridiculous thread, especially for dog lovers, spanning from Christmas season 2001 to 2011^2017)

Q. I am trying to strip my motorcycle parts down that have been poorly chrome-plated. One fellow at a restoration shop said I could eat it off best with hydrochloric acid. I asked him how to make it and he wasn't sure. Can anybody help me with my question?

Steve c [last name deleted for privacy by Editor]
- Springfield, Illinois


Muriatic Acid

Dude,

You don't just "make" hydrochloric acid.. you buy it. Secondly.. its EXTREMELY nasty stuff. Thirdly (if that's a word)..you would end up with a heavy metal acidic hazardous waste that you would need to dispose of properly. I guess, what I'm saying is..if you want the chrome chemically stripped off, please send it to a professional. There may be other, mechanical, safer ways of removing chrome off of a scooter, go to the search page, as I'm sure I've seen others ask a similar question.

Marc Green
Marc Green with Rusty
anodizer - Boise, Idaho


First things first - get a new guy for the restoration. If he can't tell you that hydrochloric acid (chemical symbol HCl) is also Muriatic Acid [linked by editor to product info at Amazon] - although not as strong as industrial grade HCl) then I might wonder about his other plating abilities. That said, it is best to let the plating shops do this type of work since they are equipped to handle the waste generated from the stripping process and can immediately replate the parts to your liking.

Hope this helps.

Dan Brewer
chemical process supplier - Gurnee, Illinois


ASM vol5
ASM Metals Handbook vol. 5

Surface Cleaning, Finishing and Coating

Electroplating Engineering Handbook

Water and Waste Control for the Plating Shop

weiner book
Chromium Plating

Weiner & Walmsley


Hi, Steve. The main issue is that "chrome plating" is actually a very heavy layer of nickel plating followed by an extremely thin layer of chrome plating. You might be interested in our "Introduction to Chrome Plating".

Hydrochloric acid (HCl) will remove the chrome quickly but will not touch the nickel plating, so the effort will not fix your poorly plated part or make it look any different. If the parts were poorly plated, the shop which plated them should fix them.

HCl is a compound rather than a mixture, so your question is similar to asking how to make water or how to make salt; it's not something you mix, it's something you react. You can make a small quantity of hydrochloric acid on laboratory scale from ingredients like sulfuric acid and salt -- but then you need to ask how to make sulfuric acid or where to buy it. So in reality it's probably much easier to buy hydrochloric acid, available in most hardware stores as "muriatic acid", than to first buy sulfuric acid and then try to make hydrochloric from it.

Best of luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Steve,

I feel real sorry for you. All these experts, which is what they ARE ... giving you very good but expensive advice. And if you become a finishing.com addict, you'll notice that quite a few of the responders need to have dogs or dawgs with them!

If you have just a few small parts then, as the man said, go to the Hardware store and get a small bottle of Muriatic acid. Sometimes it's called toilet bowl cleaner [linked by editor to product info at Amazon] or brick cleaner. The (safety) instructions are on the bottle or should be.

Get a small paint brush and a plastic bowl. Drip in a small amount of that acid. Brush the 'parts' with the acid. Then when (if!) the chrome has disappeared, flush rinse.

Dump the waste/excess acid. If clean, back into the bottle. If not, drop in some baking soda [linked by editor to product info at Amazon] (you should have some in the fridge). This will neutralize the acid which you can then safely dispose down the sink.

Mind you, the chrome glitter is just an ultra thin surface veneer. Under the chrome should be nickel and behind that copper (for bonding to the steel) ... That's what good platers do ...

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



Ted and Freeman,

Awhile ago (think back to the Hypothetical Dead Fish saga), Ted thought that there was perhaps a teacher cowering in front of Freeman's car..now I'm beginning to think it was a poor puppy dog! Not knowing a whole heck of a lot about chrome removal, I assumed he really needed HCl to remove everything, including the strikes. And that the weaker Muriatic acid wasn't strong enough. As far as just dumping the residue down the sink..I guess I get a little flustered knowing that all the accumulated household hazardous wastes in the country (paints, thinners, oils, etc..that normally just get dumped down the drain, or on the ground)probably does more harm to the environment then the industrial hazardous waste (which is normally properly disposed of).

Marc Green AND his best buddy, Rusty

Marc Green
Marc Green
anodizer - Boise, Idaho

But which dog is the most lovable?

pooky
tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania

Freeman,

What an excellent piece of advise you lent to Steve! I can just imagine the look on his face when he dumps about a half a pound of baking soda into the spent HCl/metal ion solution and it burps a load of carbon dioxide and non-reacted hydrogen chloride onto his garage floor (not to mention, his pants). I'm sure he is well versed in pH measurement, neutralization, heavy metal ion precipitation and the like; so he will, no doubt, perform the aforementioned operation with grace and skill. Comedy Central is always looking for talent; maybe you missed your calling! (LOL).

It IS, albeit, kind of interesting that there are a lot of dog pictures here!

Just giving you a hard time, Freeman! Talk to you later.

randy fowler
Randall Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA


Fellow finishers: I ask you to ponder this question...which dog is more lovable, AND can hunt? And, Randall...you took the words right out of my mouth!

Marc Green
Marc Green
anodizer - Boise, Idaho

You can't judge a book by its cover, Tom, so I can't answer your question. But I think I like beef better than I'd like either of them.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Soooooo...fellow finishers..are we to assume Ted has a pet cow in his backyard?

Marc Green
Marc Green
anodizer - Boise, Idaho

Hi Steve ... and also a Hi to all the dawg lovers.

A few pointers. I said mix some alkali with the spent acid, well, that was assuming you had some chemistry knowledge because ideally you DON'T ... Ideally you get a pail of water, dump some alkali (sodium bicarbonate) in it, then pour in the 'acid'... and you should get a 'fizz' reaction which stops once the acid is neutralized. Then pour it down the drain.

And a pointer to all those dawg lovers ... muriatic and HCl are the SAME damn thing. Didn't good ole Joseph Priestly discover this acid by mixing water with an HCl gas and gave it the name of MURIATIC based on the Latin word MURIA meaning brine. In the past other people have called this acid spiritus salis or marine acid. No difference AT ALL. In short, muriatic is the olde name for hydrochloric. OK? Do I now get a few wags? (from the dawgs I mean, not from the wags)

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada
40 odd years in trying to solve acid problems using the right plastics

The last person who neutralized acid that way was Joe Priestly himself. If you do it that way, you will get acid mist, and won't know what the ending pH is, so you will probably violate the sewerage treatment rules for your area, and it is not too safe, in any case.

pooky
tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania

Hey Marc, I figured you'd get a kick out of that one, judging from your initial response to Freeman. Thanks. Which dog is the most lovable? HMMMMMMMMM, let's see: I had a Cocker Spaniel for 11 years; smartest dog I've ever owned. But then, again, my parents own one like Tom's. I believe mom calls it her little "Shitsu" (can I even print that on this site?). So I guess I'll have to side with Ted in this case: Ribeye Rules! (hee..hee..hee). Wow, one guy writes in to ask about the formulation of hydrochloric acid, and the chat ends up talking about dogs...gotta love it! Anyway, Ted Mooney, Tom Pullizzi, Marc Greene, and, yes, Freeman Newton: you folks have a very Merry Christmas and a most profitable new year. It's a pleasure chatting with you guys.

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

First of all.. Merry Christmas to all at Finishing.com, and all that participate in this forum. I hope I'm not the only one in here taking Christmas eve off! Now.. secondly..on to technical matters.. as I'd like some clarification. I honestly can't believe that the Muriatic acid you buy in the store for cleaning concrete, etc..) is of the same strength as the laboratory grade HCl that I buy for my lab in order to do some testing requirements per an Applied Materials spec. I don't even want to open the bottle without protective gloves [linked by editor to product info at Amazon], and a respirator, as the gas is noxious, and choking. Am I wrong in assuming that Muriatic acid is a "watered down" version of HCl? Now Thirdly..after consulting Rusty..he too is a beef, ribeye lover..so..I guess..with a little hesitation, I will concede that Ted is right....sigh,,, but I just can't imagine "Bessy the cow" snuggling at my feet at the end of my bed every night!

Merry Christmas to all, Marc and Rusty

Marc Green
Marc Green
anodizer - Boise, Idaho

Hey Dawgs!

Do yer like supportin' yer master ... an' sometimes bein' stuffed an' shown off?

An' when yer master makes rude komments (like ter me, fer exampel) give him a good byte. He sure deserves it. An'sum think that haich sea ell ain't the same as muri-atic! No wonder they needs dawgs.

I usta hav' a dawg once. Short haired dax. It were a TRUE huntin' dawg... uster go inter th' woods fer 2 weeks all by hitself an' HUNT ... the dam and sire wer' pig hunters or Wildschweinh¸nde as the Krauts called 'em.

An' Marc Green is rong. That ain't no cow in Ted's backyard. That's th'sea. Fish maybe but he'd sure look real outer plaice holdin' up a DAWGFISH!

You canis lovers, you have a good year, d'yer hear!

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada

I am splitting my sides, laughing at that last entry from Freeman! Y'all 'r' a dang funny ol' boy, there, Newton! That was great.

Marc, on the subject of Muriatic vs. Hydrochloric: Muriatic acid, if I remember correctly from the University of California, is a byproduct of the manufacture of iron chloride. It is supposedly passed through qualitative filtration before "bottling" for retail. It has an 18 - 20 degree baume "gravity", while the purer HCl's (Printed Circuit Grade, etc.) are measured at about 22 degrees baume. Muriatic, as one would assume, also contains dissolved compounds of iron. A 5 mL sample of 50 v/v% Muriatic is titrated to the phenolphthalein endpoint with approx. 25 mL of Normal sodium hydroxide solution. 27.5 mL of 1 N NaOH are required to achieve the endpoint with a 5 mL sample of 50 v/v% PC Grade (22 Be) HCl.

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

Thanks for the clarification, Randall. And to think..all the poor guy wanted to know, was how to remove the chrome off his scooter! Hey Ted...perhaps we need a sub-directory on the site for just plain old BS!

Marc Green
Marc Green
anodizer - Boise, Idaho

(the New Year 2002)

Gosh I know it must be late and I know I have had too much of that Christmas Scotch I get once a year from a customer because I'm reading and responding to this letter. First of all my dog is the winner, sorry Tom, I'll forward a photo labeled as me on future replies. Second; all the advice on the neutralization of HCl with baking soda is fine but omits that only the pH will change in this possible hot and violent reaction. The chrome will still be there and in the Hexavalent state. A known cancer causing agent. Gosh.

quirt
Jon Quirt
- Minneapolis, Minnesota


Jon, Jon, Jon, Hydrochloric acid does not raise Cr+/- to it's hexavalent state. It raises it to it's di and/or trivalent state. Cr+/-requires an active (unstable) oxidizing agent, i.e.: sodium peroxide, with heat, to be raised to it's hexavalent state. The oxygen in the ambient water (which is part of liquid HCl) would not be enough to raise the atomic Cr to CrVI.

OK, Steve, just to be on the "safe" side, you will need to titrate the waste material in question against 0.1 N sodium thiosulfate, just to see how much (if any) CrVI is in it, then calculate the ratio of sodium metabisulfite to ionic Cr+, then multiply that ratio by the gram equivalent mass concentration of CrVI to determine the mass of Na2S205 to add. Then you will have to pass the entire volume of waste material through quantitative filtration, to isolate the CrOH3, before introducing the remaining liquid material to the waste stream.

How's that, Jon? (hee...hee...hee...)

I love this website!

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

Randall..I'm sure the "fellow at the restoration shop" will have all the necessary titrants and pH meter, and of course.. the filtration equipment that poor Steve (whom only wanted a little advice) will need. Do you think if we work hard enough that we can keep this thread alive till 2003? And Jon.. I've been anxiously awaiting to see the "hands down" winner of the pooch contest. Perhaps you are a little intimidated by the competition?

Marc Green
Marc Green
anodizer - Boise, Idaho

Randall, Review your chem books and the lowest energy state of chrome. It is different from most, the electrons just love to run off. Another hint Cr III is green. Perhaps dissolve a bunch of chrome into HCl, then raise the pH to 9.3 (lowest solubility) Got any ppt.? No? No kidding.

quirt
Jon Quirt
- Minneapolis, Minnesota


Hey Dawgs, Am gettin' a trifled hupset with all them damn dawg pikters I keeps seein'. (Heck, I've seen better dawgs, too!) Did yer kno that in Korea th' fayvreet dish is dawg meat ... with some kat appertizers, too. I ain't lyin'. Them those finishing.com dawgs sure look too well fed, eh? Yummy food in Korea! Maybe you're beein' fattened up. Hope not!

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada

January 9, 2002

ATTENTION! THIS letter MARKS THE END OF THE FASCINATING, IF SOMEWHAT DISGUSTING, REPARTEE ABOUT DOGS.

Thank you for your consideration and,

Sincerely,

pooky
tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania

OK, Mr. Quirt (smart alec), I will break out my general chemistry textbooks and review the nature of the element in question. Yes, I know that CrIII is (blueish) green; yes I know that CrVI is goldish orange. I am also aware that chromium chloride salt is as aforementioned. And, lastly, I know that the Cr orbital electron "acceptance" of influences is different than other atoms. I don't remember, albeit, that any of the previous entries (except yours)mentioned color. Could it be that you are now an active member in assuring that this "Entry #12044" remains active until 2003, as Marc wondered? Marc, when I listed (to poor Steve) the necessary steps for removing Chromium from his HCl liquid material, I was (as Rush Limbaugh calls it) "...illustrating absurdity by being absurd". OK, back to filling out my TURP reports for 2001! Talk to you guys later!

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

Hmm. I know that alkaline stripping (removal of chrome in electrified caustic solution) generates hexavalent chrome. In fact, electrocleaning tanks in which chrome is removed deliberately or accidentally often get a bright yellow color, like lemon icing. I think getting that color as opposed to the usual amber color of hex chrome is due to the alkalinity and chromate vs. dichromate thing.

Hydrochloric acid is an amberish color anyway, so I don't know that it's color will reveal the state of any chromium dissolved in it. Such a common and important question, and so much speculation! Does anybody *know*for*sure* whether stripping in hydrochloric acid generates hex chrome?

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Ahhh...Randall.. do you not recognize sarcasm when you see it? I surely recognized yours! Now.. on to Ted's comments..First of all, the HCl that I purchase is always clear in color, I've never seen it shaded at all. Does the actual stripping process generate hex chrome..or is it just removing the already existing hex chrome, me thinks it would be the latter? Not being too familiar with chrome plating..is it not a hex chrome solution that is used? If it is a tri-chrome solution does the addition of acids or bases somehow change it to a hex? Or does the addition of a current (as Ted mentioned) somehow play into the change? Sorry guys.. my chemistry knowledge probably isn't as vast as you'alls.

Now.. onto more important manners..Freeman..oh Freeman.. what am I gonna do with you. Them thar dawgs is meant for huntin, and companionship..NOT for eatin (now.. CATS..thats fine..bon-appetite) And Tom...the end of the dog commentary can't be completed until Jon gets around to attach a pic of his pooch. But Tom.. it is the NFL playoff season.. have you ever considered using your pooch for a football? Its about the right size.....

Good luck on the TURP report, Randall!

Marc Green
Marc Green
anodizer - Boise, Idaho

So many responses, so little time. Oh, I forgot, we have until 2003! WHEW! At any rate, let's get on with it:

1. Freeman, these fellows are obviously not (choke) consuming their dawgs; we can see their K-9's in the photos. But the litter...those poor puppies...!

2. Tom, OK, I agree we should "move on". Therefore, this weekend I am going to scan a photo of myself with...er...my CAT! Yes, it's true; a dog lover such as myself has been reduced to harboring a feline. No pussy jokes, Freeman.

3. Ted, you have precipitated a challenge. On the morrow (Friday), I shall order a certain mass of pure chromium ingots from a reliable company in New Jersey. When aforementioned ingots arrive at my lab in Boston(Monday), I am going to weigh said ingots upon the lab balance, recording displayed mass thereof. Then, I shall submerse those Cr ingots within measured, ambient, and agitated volumes of two grades of HCl (22 Be PC Grade and "Hardware Store" Grade). I will then analyze said solutions visibly, titrimetrically and spectrophotometrically. Expect the values of my results to be entered upon this site late next week. OK, I'm goin' in! Cover me!

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

 


Ok Marc I am seeking some tech help as to how to submit my photos but I assure you the Dawg photo is on the way. As to making a determination about the Chrome becoming Hex in an HCl media I'll let someone else enter the fray, Or let Randy finish his own testing. As I see this so far it is an oxidation/reduction reaction...While the chrome has been oxidized to Hexavalent, Randy has been reduced to name calling :-)

jon quirts kirby
Jon Quirt
- Minneapolis, Minnesota


Our webmaster Kate, a dog lover who has otherwise established a standard of only printing a person's picture once on each letter, has already printed Rusty's pic 5 times here. So I guess she has already decided which dog is the cutest.

I guess that contest is actually over anyway as this thread seems to be about to veer off towards who has the meanest junkyard dog rather than the cutest smiley.

I'm betting on Tom's for this round. And I'm betting on tri-chrome in the HCl, Randall; but I'd rather know than guess, so I appreciate your proposed test!

Marc: as for the color of HCl, it just goes to show that there's no substitute for first-hand experience! I've spent 30+ years visiting plating shops but never personally made up an HCl dip. So I've never seen them any color but light amber, but apparently I'm always seeing low grade acid or when there's already iron dissolved in it; it does make sense that HCl should be clear; thanks for disabusing me of an ignorance born of only second-hand knowledge.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2002)

I know, Marc. Right after I clicked on the SUBMIT button, I realized that my response was a little too "literal". We are both, apparently, card-carrying members of the American Satire camp! Secondly, Marc, a plated deposit of chromium metal is composed of neutral chromium atoms, regardless of the solution in which said deposit is plated. Direct current (electrolytic) plating turns the chromium ions that are floating and bouncing around in the tank into "natural" metal; they (the ions-turned-atoms) are neither trivalent nor hexavalent when they bond to a component base-metal. The power supply donates enough electrons to each chromium ion in the bath to balance it's charge and turn it back into "good ol' metal". And thanks for wishing me luck on the TURP. Luck is exactly what I'll need. Haven't done one of these since '96!

Now for the technical stuff. Rather than order the Cr ingots, I opted for an approach which would more accurately duplicate Steve's scenario. This morning I rummaged through the maintenance department until I found a lone, off-brand, chrome-over-steel plated socket. I then exposed this socket to submersion in hydrochloric acid, then neutralized and analyzed the acid afterwards. The results are as follows:

* Mass of socket (M1): 8.65 grams
* Mass of socket after stripping (M2): 8.45 grams
* Total mass lost to stripping process (M1 - M2): 0.2 grams (200 mg)
* Original acid volume: 25 mL
* Submersion time and temperature: 10 min. @ 22.3 °C (~72 F)
* Acid type and appearance: Printed Circuit Grade, 22 Deg. Baume Hydrochloric Acid, concentrated. "Water clear" in appearance.
* Appearance of acid after submersion time: clear yellow-green liquid
* Mass industrial grade sodium bicarbonate (NaHCO3) to raise sample pH from 0.51 to 6.92: 92.5 grams
* Volume of 1.0 Normal sodium hydroxide solution to raise sample pH from 6.92 to 9.3 (actual = 9.28): 96.7 mL
* Appearance of sample following neutralization: Dark, blue-green liquid with precipitates
* Appearance of filtered sample (filtrate): clear, with very slight olive green hue
* Concentration of hexavalent chromium (Cr6) within filtrate (spectrophotometric analysis): 0.05 milligrams per liter(mg/L)
* Concentration of Cr6, adjusted per dilution factor: 2 mg/L
* Percent (%) Cr6 of total mass lost to stripping process: 1%
* Conclusions:
1. Iron ion leached from base steel during stripping process reduces CrVI to CrIII
2. Steve needs to use milk of magnesia instead of baking soda (no acid mist liberated)

On Monday, I will analyze the prepared sample for TOTAL chromium. Any takers on whether or not CrIII is in there...hmmmm?

And people accuse chemists of having no life! HA!

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

(2002)

N...Name calling?! Oh, you mean "smart alec". Oh, OK, never mind.

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

(2002)

CORRECTION! Upon reviewing my notes, I have observed one volume discrepancy: The original volume of concentrated HCl was 50 mL, not 25 mL, as reported earlier. The dilution ratio would, therefore, be 20:1, not 40:1 as I was calculating when I made the 01/11/02 entry. This would change the adjusted Cr+6 concentration to 1 mg/L, rather than 2 mg/L (or 0.5% of the total metal dissolved, as opposed to 1.0%). All other measurements and values remain constant.

Chow!

randy fowler Randy Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA

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