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Acid zinc on top of alkaline zinc plating

2005

WE ARE DOING RACK ZINC PLATING ON STEEL HANDLES 3/16 X 25" LONG. WE GET VERY NICKEL-LIKE DEPOSITS FROM AMMONIUM BASED ACID ZINC SOLUTION(NEW SOLUTION, WITH AIR AGITATION) BUT WITH SOME ROUGH DEPOSITS ON RANDOM POINTS OF THE HANDLE(SIZE OF SAND) - CAN ANYONE TELL US WHY WE GET THIS ROUGHNESS?

SO WHAT WE DO IS WE PLATE IT IN ALKALINE BATH 10MINS THEN RINSE AND GO TO ACID ZINC BATH FOR 2MINS. WE GET THE SAME FINISH WITHOUT THE ROUGHNESS.

WILL THE 2MINS ACID ZINC PLATING HAVE ANY ADVERSE EFFECT ON THE FINISH? WILL THE ALKALINE DEPOSITS REACT TO THE ACID ZINC DEPOSITS DURING STORAGE?

THANK YOU FOR YOUR TIME

ANDREW KAW
- MANILA

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You have the very best idea. I thought the original idea was mine about 10 years ago but could not get anyone to put it into production, probably because of the cost of the extra steps.

With acid zinc we could not get heavy thickness under the head of barrel plated rivets. In the prototype line we alkaline zinc plated for thickness, rinsed, dipped through HCl, then bright acid zinc a top coat for beauty. The rivets staked great and were pretty to look at.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2005

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THE PROBLEM IN ACID ZINC ROUGHNESS MAY BE DUE TO LOW TEMPERATURE BELOW THE OPTIMUM, WHERE AMMONIUM CHLORIDE CRYSTALIZING. VERY POOR filtration ALSO MAY CAUSE PROBLEM.SINCE ammonia [on eBay or Amazon] BASED BATHS ARE HIGH SPEED BATHS ANY MINUTE FOREIGN MATERIAL WILL DEPOSIT QUICKLY. WHETHER AIR AGITATION AVAILABLE. CHECK METAL CONTENT, TOTAL CHLORIDE,AND GOOD filtration WITH GOOD ANODE BAGS MIGHT REDUCE ROUGHNESS.CARE SHOULD BE TAKEN WHILE TRANSFERRING FROM ALKALINE MEDIUM TO ACID MEDIUM WITH PROPER WASH. OTHERWISE ACID BATH PH TENDS TO INCREASE AND ALSO POOR ADHESION OVER ALK. ZINC DEPOSIT.TRY TO GET ROUGH FREE DEPOSIT FROM ACID BATH IS MUCH ADVANTAGE.

P. Gurumoorthi
electroplating process chemicals - Chennai, Tamilnadu, India
2005