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topic 56140

Determining and removing chloride in Chrome plating solution




A discussion started in 1997 but continuing through 2018

1997

Q. Looking for the best way to remove chloride contamination from my chrome tanks. I'v been in touch with our chemical supply company and also talked to a competitor about a good solution to this problem, what I heard from both of these sources was in complete contradiction to each others methods. Please advise.

Thank you,

Jeff Hanaway


Hard Chromium Plating
by Guffie
from Abe Books

or

1997

A. The best method that I have found is to do a draw off the bath.

Some people add silver oxide, but this should be done in a separate tank to ensure that the precipitated silver chloride is completely filtered out during the transfer back to the plating tank.

I have heard of people dummy plating the chloride out of the tank, but in an aqueous environment the chloride reacts with the water to form hypochlorous acid. I have not actually tried dummy plating to remove chloride, though.

One could probably remove the chloride with ion exchange resins, but that would probably remove the catalyst also.

John L. Zable


1997

A. Dummy is a good solution to chloride contamination. I do not remember the exact conditions, but I think it is done with a small cathode and high current density. I know it works. For more accurate conditions, leave a message for Jim Watts, he knows the answer for sure.

There is another possibility, to add barium carbonate. The chloride acts as a catalyst just like sulfate (actually a stronger one then sulfate) so by reducing the sulfate, you actually reduce the effect of the chloride. The chloride will decrease with time and then you will have to increase the sulfate again. It works!

sara michaeli
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel



Chromium Plating
by Weiner & Walmsley
from Abe Books

or

1998

A. To remove chloride from a chromium plating solution, you can add silver oxide or silver carbonate. Both methods are expensive due to the cost of silver salts. Use stoichiometric amounts

Electrolytic dummying of the solution is very effective, especially if the contamination is high. There are a variety of recommended electrolytic procedures and one that I am familiar with (and it works) is to Electrolyze the solution using an anode to cathode ratio of 10:1 while maintaining an anode current density of 25 ASF.

Trust this helps.

Ken Lemke
Ken Lemke
Burlington, Ontario, Canada



To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Silver Carbonate for Reduction of Chlorides in HEEF-25?

(2002)

Q. I'M LOOKING FOR INFO ON SILVER CARBONATE TO REDUCE CHLORIDE LEVELS IN MY HEEF 25 CHROME PLATING BATHS. IS IT SAFE? IS IT EASY TO WORK WITH? WILL THIS REALLY WORK? ANY INPUT WOULD BE HELPFUL.

Dean Tufano
- Rochelle, Illinois, USA


(2002)

A. Hi Dean. Since HEEF-25 is a proprietary product from Atotech, and nobody else admits to knowing exactly what is in it, I think that as the starting point should be to tell us what the supplier suggests. Thanks and good luck.

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


(2002)

A. It is Silver Oxide, not silver carbonate to reduce or eliminate chlorides. The upper limit is 50 ppm chlorides in a bath when it may begin to interfere with the sulfate/chrome ratio. 150 GRAMS silver oxide added to 1,000 gals. chrome bath reduces chloride 20-30 ppm. Hope you are sitting down when you obtain the price for silver oxide. No it should not interfere with the HEEF process.

William F. Hemp
- Grand Rapids, Michigan


(2002)

A. Hi Dean, to clean your electrolyte from chlorides, it is much cheaper and easier to work it out by dummy-plating. Putting silver-ions into the electrolyte precipitates AgCl AND AgCrO4. You get a lot of sludge and it is a very expensive treatment.

Best regards,

Michael Hekli
Switzerland


(2002)

Q. Dear Mr. Michael Hekli,

Can you be more clear about dummy plating. It sounds interesting to me.

Thanks in advance.

VIKRAM [last name deleted for privacy by Editor]
- INDIA


(2002)

A. Dear Mr. VIKRAM,

For this kind of dummy plating you take a steel sheet or some steel rods and plate them with high current densities at your normal plating temperature for some hours. Then you work the chlorides out. It is not fast, but it works. You should control your effort by some chloride analysis.

Best regards,

Michael Hekli
Switzerland


(2002)

A. I agree with Michael, dummy plating is the right treatment for chloride contamination.The treatment with silver is very expensive. As for the silver reaction, well it is true that you get Ag2CR2O7 at the beginning but after a while all the chlorides will precipitate and give AgCl before any silver ion precipitates the chromates. Just as with Barium carbonate addition, at the beginning Ba2Cr2O7 is formed as there are a lot of chromate ion and much less sulfate but it will shift towards the sulfate and create BaSO4.

Sara Michaeli
Sara Michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel



(2002)

A. Hi,

I'm agreed with both Sara and Michael how to remove chloride. The cathode area must be lower than anode area. Also check the temperature because this will be very high if you not have a automatic cooling system.

Regards,

anders sundman
Anders Sundman
3rd Generation in Plating
Consultant - Arvika, Sweden



(2003)

Q. I AGREE DUMMY PLATING WILL REMOVE CHLORIDE IN HEEF 25 BATH. BUT HOW MUCH CHLORIDE AND HOW MUCH TIME REQUIRED TO REMOVE AT WHAT CURRENT?

SELVARAJ V
- Coimbatore, TN, INDIA


August 7, 2009

A. Dear Selvaraj,

Removal of chloride requires a very high over voltage. Easy way to achieve this is swap the anode/cathode connections and place a former round Pb/Sn at the former cathode point. About 4 A/Sq in will exponentially reduce the chloride by about 20 ppm in 1st 2 hours.

Good Luck,

Ken

Ken McGowan
- Dublin, Ireland



To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Why use silver nitrate in chrome plating

2006

Q. We have recently lost our chemist and have determined that he was using an amount of silver nitrate in our chrome plating baths. We primarily plate cast irons and steels. No one is sure why silver nitrate is added or what it's effect is on the coating process. Any ideas?

Mark Elloff
Laboratory Control - Baltimore, Maryland


2006

A. Silver salts are sometimes used to overcome chloride contamination but not silver nitrate as the nitrate can cause the chromium deposit to turn dark.

Sara Michaeli
Sara Michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel




High current density dummying to remove chloride from chrome plating bath

2006

Q. Hello,
I'm an employee of a small plating company.
Can somebody help me on how to remove chloride from my chrome plating tank? My chrome has a little rainbow stain problem; after I check it in the lab, the composition of Chromic acid:Sulfuric acid ratio (134 : 0.9 gr/ltr), and chloride was too high.
What problems are caused by chloride too high? How to remove it?
Thanks a lot everybody.

Setiadi
gift for my home industry - Bandung, Jawa Barat, Indonesia


2006

A. Chloride contamination will lead to hazy, milky, or even no deposit. You can add in silver carbonate to precipitate out chloride as silver chloride while carbonate will turn into carbon dioxide and water.

David Shiu
David Shiu
- Singapore


2006

A. I think dummying at 1,000 ASF will remove chloride as chlorine gas at approximately 160 °F. Try it with good ventilation; the gas is very nasty. You can also precipitate it out with silver oxide. High chloride can cause dull or hazy deposits in high current density areas among other things.

Good Luck

Trent Kaufman
Trent Kaufman
   electroplater
Galva, Illinois



2006

A. Use small cathode surface area (4:1 anode to cathode ratio works well) heat solution to 150 °F dummy between 300-800 ASF; use light air agitation to help circulate solution. 4-6 hours will usually reduce chlorides by 10-20 ppm.

J. Ott
Plating Shop - Harrisburg, Pennsylvania



Analysis for chloride in chrome bath

November 9, 2010

Q. Hi all,

I'm working in a lab, just started analysis on chrome plating solution. I've tried to determine the chloride content in Chrome plate. The silver ring on the electrode was dissolved after a few titrations, and recovery of standard check is no good.

Is there any method other than titration available for the determination of Chloride in Chrome plating solution?

Yap Huiwen
chemist - Singapore


November 15, 2010

A. ion chromatography

Terry Tomt
- Auburn, Washington


November 15, 2010

A. If you are just checking to make sure that you don't have too much chloride as a contaminant in your chrome solution, I think the easiest method is a titration; but you don't need an electrode- just a good eye and some good clean glassware. I'm feeling generous, so I'll just give you a method that I have used for years.

Pipette 10 mL bath sample and 40 mL of 25% nitric acid into two 125 mL Erlhenmeyer flasks. Set one aside as a turbidity reference. To the other add a few drops of 0.1 N silver nitrate. Carefully titrate this solution (in fine, precise increments) with standard 0.010 N mercuric nitrate from turbid to clear. Add a few more drops of silver nitrate, if the turbidity returns, continue the titration back to clear. Repeat that step until the solution no longer turns turbid. Chloride ppm = 35.6 x mL of 0.10 N mercuric nitrate.

Jon Barrows
Jon Barrows, MSF, EHSSC
Springfield, Missouri



November 16, 2010

A. Use RO or DI for make up and for water additions and you will eliminate the chloride problem as trace amounts for chlorine gas at the anodes.
This assumes that you are not using HCl to activate the metal.

James Watts
- Navarre, Florida



September 3, 2014

Q. Hi.Thank you for your tips. Really a great help to me. In the dummy method for removing chloride, is a metal rod or sheet metal better to use?

elham bolouri
- mashhad.iran


Electrodeposition of Chromium from Chromic Acid Solutions
0-15V 0-5A

August 2014

A. Hi Elham. I think a small sheet would be good. Its surface area should be 1/4 of the surface area of your anodes according to J. Ott's posting. Dubpernell's "Electrodeposition of Chromium from Chromic Acid Solutions" =>
notes that the lead dioxide on the anodes is what converts the chloride to chlorine gas ... so perhaps the shape of the cathode isn't critical? Dubpernell also implies that you can't get all of the chloride with dummying, and may still want to precipitate the final small amount with a silver salt.

Regards,

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


September 14, 2014

Q. Hi Ted. I have a low surface area of the cathode was used to eliminate chlorine and chrome plating conditions were better. With silver nitrate salts, is other than the chloride precipitated?

elham bolouri [returning]
- mashhad.iran


September 2014

A. Hi again, Elham. I've never operated a chrome plating line -- all I know is what I read in the papers :-)

Sara Michaeli says other salts are preferable to silver nitrate; David Shiu suggests silver carbonate; Trent Kaufman suggests silver oxide. And, yes, Michael Hekli says silver chromate is also precipitated. Good luck.

Regards,

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


September 15, 2014

thumbs up signHi ted. Thanks for guidance.

elham bolouri [returning]
- mashhad.iran



April 25, 2015 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Dear all,
Can someone guide me how to remove chloride from hard chrome plating electrolyte. I found a few suggested that dummy plating also removes chloride. But there is a difference of opinion. If it is possible, what is the exact procedure?
If not, will a porous pot work well to remove chloride.

V THYAGARAJ
Hard chrome plating - Bellary, Karnataka, India


April 2015

thumbs up sign Hi THYAGARAJ. We appended your inquiry to a thread which covers the subject exhaustively over a period of more than 17 years. I'm sure it will answer your general questions -- but get back to us with any remaining thoughts. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


May 15, 2015

In my opinion, heat up the solution to around 100 °C for an hour and well agitate; will decrease chlorides as chlorine gas with dummy plating sheet.

Aftab Jahangir
Aftab Jahangir
   chemist
Karachi, Pakistan




Adding Chemicals in HEEF-25 Hard Chrome Plating

June 19, 2018

Q. I Just joined to this field, as i don't have any previous experience in chrome plating
it is so difficult to understand whats going on here also no one here is to support me as well.

My question here , I have got lab report for Chrome plating tank chemical analysis
Tank 1 - Capacity 3000 Litre
Chromic Acid- 183
Chlorides - 0.2 g/l
Density- 1.079 g/ml
Sulfates 37 g/l
Copper 7.9g/l
Iron 1.8 g/l

Tank 2 - Capacity 3000 Liter
Chromic Acid- 273 g/l
Chlorides - 0.1 g/l
Density- 1.094 g/ml
Sulfates 37 g/l
Copper 11g/l
Iron 2.7 g/l

I am using HEEF 25A as catalyst, what are the chemicals should be added in tank?
how to calculate the amount of chemicals to be added? how to maintain the chemical ratio

Regards,

D.K.Francis
Shop Employee - UAE


July 13, 2018

A. Dear FRANCIS,
If your lab report is right you are in deep soup.
CHROMIC ACID around 250 gm/lt.
sulphate 2.5 gm/lt
Density 1.180 ( In your tank 2 density cannot be 1.094 that too in gm/lt. if chromic acid is 273).
All impurities like iron, copper well below 2-3 gm/lt.

Once you achieve this call the ATOTECH rep to do dosing for you.

Hope this helps.

vikram dogra
Vikram Dogra
Irusha India - Chandigarh, India



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