Metal finishing Q&As since 1989

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Photos of Zinc Plating for QC?

2001

Hopefully someone can help. I am looking for any information on plating quality especially zinc with a clear chromate finish. Is there any books available that have photos of the different surface defects, etc.

Second question, Is it normal for zinc plate with the clear chromate finish to mark with finger prints from handling? These finger prints then show up "yellow".

Any help will be greatly appreciated.

Shirley Powers
Comair Rotron - California

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2001

Shirley,

The type of defects you may encounter with Clear Zinc are:

barespots - poor adhesion of the chromate

stains- poor drying

contact loss- black marks

dullness

The Clear Zinc shouldn't mark easily, and yellow zinc should not be visible at all if you're plating Clear.

Regards,

Joel Garcia
- McAllen, Texas

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2001

Shirley,

It is imperative to wear gloves when handling zinc chromated parts to avoid the situation you describe. Your skin contains oils, acids and salts that will attack the chromated surface of the zinc. Remember, zinc plating is corrosion resistant not corrosion proof, clear zinc (type III) is the least resistant of the chromates.

So often parts failure is due to poor handling of finished parts, and not just zinc but all metal finishing. After plating many parts go to other processes such as hardware or assembly. I have seen parts fail in the field that have big hand prints all over them.

I hope this helps!

Bill Grayson
- Santa Cruz, California, USA

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My information is for Shirley regards to Yellow finger marks.

My company is a volume producer of Zinc plating in the UK.we specialize in the zinc Plating using all passivations for the Electronics industry .We have seen this problem occur many many times.The problem seams to be the finish items are handled more often by the end user (whilst the plating company gets the blame).In our own experience was to use cotton gloves at all stages of handling. This is paramount .However, we as a company always advise (subject to Conductivity) to post treat with a water based Lacquer.This not only unifies the colour to a consistent silver finish but is easily wipeable if finger marks are found .Other benefits of this treatment is that you get perfect matching parts at all times and a marginal increase in the corrosion protection.

Steve Pendleton
- Staffordshire, England
March 2, 2008