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Bright Luster vs. Matte Luster in Zinc Plating
Q. My company is purchasing steel bushings (SAE J403 1022) plated zinc with clear chromate per ASTM B633-SC2-Type III Bright luster specified.
The product we are receiving has a bright clear to light blue finish.
Our customer is requesting a matte finish due to optical inspection issues.
We have been told in the past that the zinc plate with clear chromate can be either luster and we just needed to specify the luster requirement on the drawing.
We are now being told that we cannot get matte luster with this plating and finish.
Trying to break through the myths and understand what is or is not possible with this specified finish.
Manufacturing Engineering - San Diego, California, U.S.A.
May 19, 2009
A. With certain types of zinc plating chemistries it is possible to develop a semi bright or reduced luster finish. One problem is that work that is plated in bulk (barrel) has a tendency to self burnish as the barrel rotates. This causes a brightening of the plated finish that is not possible to eliminate. Further, the chromate finish (clear/blue) generally uses chemistry that chemically polishes the plated finish. Therefore, yes it is possible to find a plater who can do a low luster job but not everyone can do it. It becomes more difficult to find someone to do the job if the chromate must be RoHS compatible.
Gene Packmanprocess supplier - Great Neck, New York
May 23, 2009
A. There are matte zinc finishes. So far I have only seen these used in the Window Fittings Industry. The process is an alkaline matte zinc + trivalent chrome passivation + sealant. Sometimes the sealant has an additive to increase the "matte look". Overall the parts look like a satin nickel style look.
I agree that your problem will be in finding a plating shop that offers this type of finish. Normally job shops are offering a bright alkaline or acid zinc. I have never seen a jobshop that offers "matte" zinc. It also depends upon how big is your production and if it is worth the pain and investment for the job shop to purchase the required chemistry.
- Budapest, Hungary
May 27, 2009
A. Dear Friend,
Generally acid zinc plated components are brighter and alkaline chemistries are a bit dull. We can adjust the brightness by dosing more brightening additives. Also, the more the thickness the brighter the component will be. So stick to your lower thickness spec.
Also after passivation use a clear top coat with higher concentration >50%. This is to reduce the luster. But make sure you don't produce runner marks of the sealers if it is not desired.
Regards
plating process supplier - Bangalore, India
July 13, 2009
How to do matte acid zinc electroplating
Q. I have electroplating equipment and material company in Iran. I have to make an electroplating line for iron bars like roto part (roto: company make a window part). I have an acidic electroplating line in my company and standard color for this part is matte. I am working the electroplating line this way: hot degreasing, acid, acidic zinc plating, citric acid , blue passivation, dry ... but it is not standard; I use citric acid for matte color and this process is not standard. My question: is there a standard way for matte color? And how I can found a way to matte color like roto parts with acidic zinc in my electroplating line? Please answer me as soon as possible.
Thanks a lot.
Good regards,
Mahdi
electroplating equipment and material - tehran, iran
November 29, 2015
A. Hi Mahdi. We appended your question to an existing thread on the subject. Less brightener and a matte topcoat seem to be two of the keys.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2015
Q. Thanks a lot for your answer. But if I do less brightener for acidic galvanization, is corrosion resistance reduced because of the zinc structure?
mahdi hasouninovin poushesh - tehran, iran
November 30, 2015
A. Hi Mahdi. I don't think reduced brightener will have any effect on corrosion resistance, especially with a top coat.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 2015
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