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Cyanide-free alkaline zinc plating: KOH vs NaOH-based

Hello,

as our company is looking for an alternative for cyanide zinc we are thinking of alkaline zinc. Our chemicals providers are divided into two, one half says that NaOH based is better and the other half says that KOH based is better. Both sides say that among their clients are companies that have just changed one process for the other as the other is better. So if anybody has had experience with both of these processes can compare them?

All the best from sunny Estonia

Joosep Poom
plating shop employee - Tallinn, Estonia
March 30, 2011

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April 4, 2011

Dear Sir,

Understood that 2 type of alkaline Zinc, NaOH & KOH,
From my point of view KOH has better performance in terms of brightness (close to Acid Zinc), higher Current Efficiency close to 85% (NaOH can reach 75% a good one), so KOH has faster speed, higher conductivity, less Voltage for the same Amperage (saving electricity cost)
In my country KOH price 3 times than NaOH, so become more expensive to run, but other country KOH price just 50% more, I think running KOH has more beneficial.
KOH need higher concentration up to 170 g/l KOH, but NaOH bath only need 120 g/l.
So, some supplier they supply additive that can be used both for NaOH & KOH bath, but on other hand other supplier only supply additive for KOH but could not be used in NaOH or the other way around.

The choice is up to you and please check the price of KOH compare with NaOH in your place.

Good luck,

Tony Chandra
- Jakarta, Indonesia

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Great answer, Tony. Thanks!

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 4, 2011

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Everything Tony wrote is correct BUT if your cleaning cycle is not perfect, stick to the NaOH.

With KOH one MUST work with higher current densities than with NaOH. So if your rectifier is not big enough, forget the KOH.

The main advantage of KOH is with barrel plating. For rack, don't bother.

Sara

Sara Michaeli
Tel-Aviv-Yafo, Israel
April 6, 2011