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ROHS compliant Black Zinc brightness

We are moving towards RoHS compliant (trivalent) Black Zinc. How do we achieve the bright black of the hexavalent Black?

Edwin Blackwelder
metal finishing - Altamonte Springs, Florida, USA
2006

Some suppliers on the AESF meeting circuit are explaining why good bright blacks are not yet available in trivalent chromate, Edwin. Other suppliers are prominently advertising total success. Usually the truth is somewhere in between; but I doubt that anyone can give you cookbook instructions to achieve what major suppliers admit that they haven't been able to do.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

Cheat. Oh I mean use a black top coat aka black lacquer over trivalent black/non chromate black. Actually the final use and corrosion requirement are instrumental in deciding what to do. Despite what may say, the technology to CONSISTENTLY produce a bright black in a cost effective manner from a trivalent product, is not presently available.

Gene Packman
- Great Neck, New York
2006

Dear Sir,
I wanted to know whether Zn- Black trivalent plating is yet established or not if yes, what is recommended process.

Amarnath Mallick
- Noida
2006

Trivalent Black Zinc (Color Problem)

Q. Hello,

We are currently acid zinc plating some parts with a thickness around 8 to 12 micron and then passivate them with Pavco's "HyproBlack" and then we apply a sealer.

We can achieve a greyish almost black color, but customer wants a jet black glossy color appearance.

How can I achieve that? Do I need a black topcoat?

Diego Mora
Buyer - Tijuana, Mexico
September 23, 2019

A. I use the hyproblack 3000 and it is jet black if everything is up to snuff. Had an iridescence problem once -- it was a contaminated sealer.

Make a new batch in a beaker [beakers on eBay or Amazon] of chromate and sealer and see what it looks like. My guess is (if there is enough chromate) you are low on part B or you have sealer issues.

But mine is over alkaline zinc. This may not apply most likely.

I use an Atotech Tridur process on acid chloride that is jet black.

Trent Kaufman
electroplater - Galva, Illinois
October 7, 2019

Thanks for your feedback, I will try to make an alkaline zinc solution, I might have better results.

Diego Guerrero [returning]
International Manucturing & Finishing Co. - Tijuana, Mexico
October 14, 2019

adv.
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