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Instant Black Spot Even Before Drying Process

April 1, 2009

Hi,

My name is Harun and I am working in a plating workshop in Indonesia. Recently, I have a problem that I have not an answer for it. I am plating on wheel axle for motorcycle, which is a high carbon steel, hardened and tempered steel.

This problem occurred recently which had not happened before in my workshop. There are instant black spots (which leads to white rust) on the thread of the axle. This black spots are noticed even before the drying process. I tried every possible way to make the part as clean as possible before plating process.

Is there any logical explanation for this event? I am in a state of confusion. Thank you.

Harun Harun
Plating Shop Employee - Jakarta, Indonesia

Hi, Harun. I don't know what metal motorcycle axles are plated with. Could you fill us in on that?

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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April 3, 2009

Hello,
Here are the additional informations:

1. The metal is plated on alkaline cyanide free zinc plating.

2. After further investigation (using electronic microscope), we found that the black spots are actually: zinc layer peeled off from the metal.

so after those facts we assumed that our pre-treatment process might not do their job efficiently. But after tons of trial and errors, the problem still exists. So I would like to ask some advice or from anyone that had this experience before. Thank you

Harun Harun
- Jakarta, Indonesia
April 14, 2009

Hi,

Please check the base metal, I guess its very porous , try out the acid zinc process,then heat components, do again a low thickness of plating then passivate.
To be practical work at lower current density.

Praveen Kumar
plating process supplier
Mumbai, India
April 17, 2009

April 21, 2009

Hi,

Thank you Mr. Kumar, I tried the process in Acid Zn (barrel) and it worked just fine. Are there any explanation why it worked fine in Acid Zn? Since my background is mechanical eng. so I did not get the reason.

Thank you

Harun Harun
- Jakarta, Indonesia

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