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topic 36025

Remove / Strip Zinc Plating from Steel


2005

Q. Hi.
I work in roll manufacturing company. Recently I got a job about removing plated zinc on steel roll. Roll Dia. is about 30", face length is 54" and about 80" long including shaft.
Zinc is plated over the entire roll. I don't want any hazardous method, which causes my workers to get sick or makes the environment poisonous with zinc oxide.
I decided to heat the roll in tampering furnace to 450 °C (790 °F) and melt the zinc (Melting point of zinc is 780 °F). I will appreciate any comments, suggestion, other easy methods, or advice.
Thanks.

Kashif
Manufacturing Co. - Chicago, Illinois, USA


2005

A. Kashif: Stop please.

That sounds like an ineffective method to strip zinc from steel because the zinc plating is thin, and the steel will remain "wetted" with it; plus, it's possibly dangerous, environmentally questionable, and expensive :-)

"The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins . . ."
H. L. Mencken

Opinion! Rant mode on: Such ideas are, of course, the harvest of the chemical paranoia that our governments spend so much of your tax money sowing. Rant mode off.

Although welders who weld galvanized steel without proper ventilation can inhale clouds of vaporized zinc and get a serious overdose, resulting in metal fume fever, zinc is an essential nutrient -- not a poison. Cold prevention tablets are zinc salts.

Zinc is readily and almost instantly stripped in relatively mild acids like inhibited muriatic acid (hydrochloric acid). And other methods like reverse plating are not difficult either if acid immersion is inappropriate for the steel of this roll. My question is: who applied the zinc plating? If it was not done in house, then probably the stripping should not be done in house either. Any plating shop capable of zinc plating rolls will be capable of safely stripping the zinc plating. Best of luck.

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



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.



2005

Q. What is the best way to strip Zinc plating, leaving the Sheet steel substrate in a condition where it can be re-plated?

Peter Francis
Design Engineer - Chelmsford, Essex, UK


2005

A. Immersion in a hot caustic solution or room temperature hydrochloric acid will remove the zinc. Your electroplating contractor should be able to do this prior to replating.

Dougie Lightfoot
- Fife, Scotland



How to remove zinc plating from steel bolts

2006

Q. I would like to know the process to remove the zinc plating from some bolts. This is needed so I can paint them for an old car restoration.

Jim Butterbaugh
Hobbyist - Tijeras, New Mexico


2006

A. Zinc is quickly stripped in Muriatic Acid [linked by editor to product info at Amazon]. However, this acid is somewhat dangerous for an untrained consumer, the fumes can ruin any metal nearby, and you'll be left with a hazardous waste to deal with. There is also a good chance of hydrogen embrittlement of the bolts. Better would be to find painted or black oxided bolts, and if that isn't possible, to send them to a plating shops for stripping (may cost more than you like). Best of luck.

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



Will electrolysis (reverse plating) remove zinc plating?

2004

Q. I wonder if it is possible to strip the zinc layer from zinc plated bolts by electrolysis in a profitable way.

I have to strip zinc plated material, but I want to find another ways rather than just using sulphuric acid. Therefore I wondered If it is possible strip this material in a zinc plating electrolyte meanwhile I connect it to the anode instead to the cathode?

What would be the risks and the damage to the substrate material (steel) by doing this way?

Thanks a lot and my best regards.

Guillermo Castorena
Plating Shop - San Luis Potosi, SLP, Mexico


2004

A. We use HCl to strip zinc from steel. You can use sodium hydroxide too. Why use power when it's unnecessary?

Steve Clark
- Belfast, Maine, U.S.A.


2004

A. Acid stripping is bad news for hard bolts. Hydrogen embrittlement is a very strong possibility. Bake (soon) after strip if you do. Caustic is slower than acid, but it also has a lot smaller risk or attacking the steel. Electrolytic will speed up the operation, but costs more-- a tradeoff.

James Watts
- Navarre, Florida



Stripping zinc plating in preparation for E-coating

March 10, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi All,
I got some parts with zinc plated surface and customers would like to remove the surface and replace by E coat. Currently I'm using HCl 30% to remove the zinc layer but it is too strong, and residue leftover causes high rejection. Can any Mr. Expert give me some guides or better methods?
Thanks

KC Tan
- Ulu Tiram, Johor, Malaysia


March 2014

A. Hi KC. We appended your inquiry to a thread which suggests some other methods, but my question would be why do you need to remove the zinc plating? If the plating is not defective, I think it can be a good base for the e-coating, and will offer sacrificial protection. If you remove the e-coating, you will have to phosphatize the surfaces before e-coating. Good luck.

Regards,

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


March 11, 2014

thumbs up signGreetings Mr Ted,
I understand your concern but customer insists on cosmetics. This zinc layer if not removed will form "wavy" surface after E-coat, which is considered as NC regardless how good the adhesion.
Thanks

Kc Tan [returning]
- Ulu Tiram, Johor, Malaysia



Can I use NON Fuming HCl to strip reusable zinc plated steel parts?

May 30, 2014

Q. We would like to use a lower concentration of HCl that is NON fuming for the safety of our personnel. I would like to find out if the bath will still be strong enough.
We are currently using 110 gallons of 20 baumé and 160 gallons of water.
If we can, are there any recommendations of concentration and quantity of the HCl and the amount of water to add.
Thanks.

Daniel Andreson
Plating shop - Oklahoma City, Oklahoma, USA



October 19, 2018

Q. Possible to use Citristrip to pull zinc plating off screws? Need to patina the heads after zinc removal. Thanks!

R. Anders
fabricator - Oakland California


October 2018

A. Hi R. Anders. The SDS for Citristrip [linked by editor to product info at Rockler] mentions only organic chemicals, rather than acid or alkali, so I doubt that it will work. But there's a saying among bridge players that "a peek is worth a hundred finesses" : some things are easy enough to find out that it may not make sense to spend a lot of time in speculation :-)

Regards,

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


October 22, 2018

Anything with "Citri" in the name generally contains either citric acid or d-limonene (a.k.a. citrus oil). Citristrip calls itself a paint and varnish remover, which says "solvent" to be, which of the two options would be the d-limonene.

Citric acid and citric acid based products aren't that difficult to come by, though, nor is citric the only option for stripping zinc. Any mild acid should work fine, including acetic acid (a.k.a. vinegar).

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner



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