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topic 34321

Differences between chloride (acid) and alkaline zinc plating

A discussion started in 2005 but continuing through 2018



- Sugarland, Texas


A. First, I presume a typo and you mean "chloride" zinc (not "chlorine"). Deposits from the acidic chloride and those from alkaline baths exhibit different traits in terms of ductility, speed of deposition, ability to be post treated, etc. You need to do a little research since what you are asking for is too difficult for me to answer in this forum.

Gene Packman
- Great Neck, New York


A. John

Unless you mention which components are intended to be plated, a choice or suggestion is difficult.

Stay with alkaline for good distribution and excellent ductility. Slightly lower costs.

Stay with chloride zinc for good productivity and if the materials are hardened or High carbon steel.

There are more points but we need know what you are plating first.


Asif Nurie
- New Delhi, India

With deep regret we
sadly advise that
Asif passed away

on Jan 24, 2016

"Zinc Plating"
by Herb Geduld
from Abe Books
info on Amazon

2005 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. My first question may sound very simple but I am trying to establish exactly what the difference is between Acid Zinc plating and Zinc Cyanide plating. Is there a difference in the corrosion resistance (especially in salt fog) or plating thickness range or maybe one is suited to yellow passivate and the other to clear, etc.

Secondly I have been asked to quote for a product which is to be DIN 50962 FE/ZnCo 12 //C plated. I would like to know what type of plating this and what would be the cost difference between it and more standard plating processes such as those mentioned above.

Roy Devitt
- Gort, Galway, Ireland

A. For practical purposes there should usually be little difference to the end user between a zinc plated part that was successfully plated in acid zinc vs. cyanide zinc. But please review the previous discussion on this thread. The shop applying the coating will make a choice of which process to implement based on a number of factors involving cost, waste treatment and disposal, required covering power, brightness, etc.

Zinc-Cobalt is an alloy plating and is a different matter. I can't quote prices since I am not a plating shop, but the alloy plating is more expensive for the shop and more difficult to run; so it will cost more, but probably not outrageously more. Wild guess 10% to 50% more depending on whether the plating shop would rather do alloy plating or would rather not :-)

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

April 17, 2012

Q. Why and How does Alkaline Zinc Plating improve the Ductility over Acid Zinc Plating Process?

- Jamshedpur, Jharkhand, India

April 17, 2012

A. Hi, Arijit.

It's very complicated, but the metal crystals are growing from a very different solution, and actually grow differently. Alkaline zinc crystals are smaller, and have less tensile stress.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

April 20, 2012

Q. Without using a Sealer during Plating Process, how can we increase the White and Red rust corrosion life of Zn plated components in a vehicle? What type of Air drying product should we apply on plated components having Scratch and damage marks?

Second Question is: We are getting Red Rust first on Bent portion of the Zinc Plated parts, is it because of plating film cracking? Plating Thickness is only between 8 to 13 micron.

Can we consider Trivalent Chrome passivation over Zn plating as having better corrosion resistance than Hexavalent Chrome Passivation? What is the reason behind that? Trivalent Chrome has no self-healing properties.

- Jamshedpur, Jharkhand, India

April 22, 2012

A. Hi Arijit.

Trivalent chromate is a highly proprietary process. Some vendors' processes include a sealer, others don't. If you want to skip the sealer, you must pick a vendor who offers a system that doesn't use a sealer -- you can't just leave out a step. The plating thickness sounds reasonable, but alloy plating would offer more corrosion resistance than plain zinc plating.

Plating can crack at bends if it isn't ductile enough, but it shouldn't; an alloy plating like tin-zinc might be more ductile. You are correct that trivalent chromates are not self-healing. Trivalent chromating complies with RoHS requirements, which is vital, but it is not superior to hexavalent in corrosion resistance.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

November 18, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. We are plating for some parts in Rack.
we need to know which is best and what is difference between Non-cyanide and Chloride for rack plating.
Which one we can be recommended for rack plating?

Siva Kumar
Buyer - Tamilnadu, india

November 2014

A. Hi Siva. We appended your inquiry to a thread on the subject which should offer you some insights. Acid zinc is brighter, but alkaline zinc offers measurably better throwing power, which can be important for rack plated work. Acid zinc holds some disadvantages for the plating shop, like being very corrosive, while alkaline zinc has its requirements and quirks as well. Alkaline zinc is probably growing in popularity while acid zinc is waning.

If it doesn't matter to you, don't specify either, so you can keep your options open. If you feel you need to specify one over the other for reliability and duplicability, make sure you have available suppliers for the process before limiting yourself.

Luck and Regards,

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

January 18, 2015

A. Alkaline zinc's efficiency is approx. 50%. Acidic's zinc efficiency is close to 100%.
BUT metal distribution is much better in an alkaline plating solution.
Cast iron MUST be coated in an acidic zinc plating solution.

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

April 13, 2015

Q. Hi all,
Can anyone suggest which plating process (acid vs. Alkaline) gives better results in welding (Spot welding of studs)?

C Saravanakumar
engineered fastening - Chennai,Tamilnadu, India

May 1, 2015

A. Alkaline zinc plating is more suitable for fasteners.

Karthikeyan Ponnusamy
- Bangalore, Karnataka

May 2015

thumbs up signHi Karthikeyan. I am not disagreeing with you, but I ask what property of alkaline zinc plating makes it more suitable for fasteners in your mind? Especially since it seems less suitable for hardened parts and many fasteners are hardened. Thanks.


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

January 10, 2016

Q. There isn't much difference between acid and alkaline plating in terms of corrosion resistance as far as fasteners are considered. The shapes are simple. No such requirement of throwing power.
Acid plating gives better aesthetics and efficiency.

waqqar aslam
Pantnagar - Rudrapur, Uttarakhand, India

January 28, 2018

Q. Which process is cheaper? NC Alkaline Zinc or Acid Zinc?

Vishal Dalvi
- Goa, India

February 5, 2018

A. Hi Vishal,

Usually acid zinc plating is cheaper, as it has more efficiency and lower maintenance costs. But alkaline zinc plating has improved its efficiency and costs lately, so it's difficult if you don't have the part to decide.

For fasteners, acid zinc plating is more versatile and universal. For hardened parts it's the only way to deposit zinc in less than three hours.

For sheets and large parts, alkaline zinc plating is the only way to achieve homogeneous thickness.

So, it depends on how and what you plate :)

Best regards,

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

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