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Ted Mooney, P.E. RET
- Pine Beach, NJ

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Blackening Hot Dip Gal/Bright Zinc Parts

Q. Howdy,

I have a project coming up where I need to blacken/darken a large range of zinc-coated parts - I can either have them in hot dip gal, or bright zinc. Parts themselves are steel. They don't need to be particularly corrosion resistant or uniform, but all need to be black as it's part of a large exhibition piece. Paint isn't an option.

Previously I have removed zinc coatings with muriatic acid, then heated in a kiln + quenched in oil. I tried it without the muriatic acid step and it turned out garbage. It's worked fine, but for this job there's probably about 100 fasteners, around 50 large brackets and numerous other small parts, so it would be incredibly time/labour consuming.

Is there a chemical bath or easier process that would work? I've asked a local blacksmith, and he said the oil quench process was the only one he knew of. If it's anything that's less toxic that would be a great benefit.

Thanks

D Spriggs
- Brisbane QLD
June 25, 2024

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A. Hi D.,
Ideal would be to just order the parts zinc or zinc-iron plated and black chromated if they're not already on hand. Blackening them later is not as easy and reliable. If you have the luxury of ordering what you want, black nickel plating and hot or cold black oxiding are other alternatives.

You may be able to blacken zinc plated or galvanized parts with mundane zinc blackening solution.

This question has been asked & answered a few times over the years; please see:

• thread 29924, "How to darken zinc plate and galvanized materials" and
• thread 59756, "Need DARK galvanising alloy. What is black galvanizing?".

Luck & Regards,

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

Thanks - have read these and dozens of similar posts, and there has always been suggestions that things 'should' work but never any real confirmation that anybody had actually done it.

Unfortunately I can't order any of the parts in black chromate or this would make my life much easier.

Cheers

D Spriggs [returning]
- Brisbane QLD
June 27, 2024

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