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  for Metal Finishing since 1989
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Dents on Electroless Plating Surface

2005

My factory makes steel(SPCC) components used in Hare Disk Drive. The thickness of nickel is 5 to 8 micron done at plating supplier. The problem is that the rusty found at the dent area. (Dent is from tumbling or poor handling). I use copper sulphate ⇦this on eBay or Amazon [affil links] Test to see if there is iron on the surface. My questions are:
1. How do I know the dent occurs before or after plating?
2. Can I fix the problem by plating process if dents occurs before plating?
3. Is copper sulphate test a correct test method?
(Before I use it for test SUS passivation)
4. Is it easy to break the 5-8 micron nickel coating?
Thanks for your information in advance.

Fred Ho
Thaixon Tech - Bangkok, Thailand

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2005

If the rust problem is only at the dents, they most likely are the result of mechanical damage after plating. The ductility of electroless nickel is low (only about 1.5% at best) and the coating will break if deformed mechanically.

The only way to confirm whether the dent occurred before or after plating is by microscopic examination.

A ferroxyl test is usually a better test for porosity than copper sulphate. See ASTM B733.

Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.