The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Pin holes in chrome allow corrosion

2006

I am buying a plastic product that is triple chrome plated (copper, nickel, chrome)

After a while in the field I am getting spot corrosion of the copper through the chrome. My guess is that a pin hole through the chrome exists and the copper is exposed. How can I prevent these holes?

Best

A W Gebhard

---

You shouldn't build onto a shack, and you shouldn't try to 'fix' the effects of corrosion on inadequately plated parts, A W. Top quality plating on plastics, such as is used on automobiles, can last decades in the harshest environment. The plating on your parts may have been designed for interior use, and isn't up to the actual demands; you need to step up the spec. I suppose it's also possible that the plastic can't withstand the heat of the lighting, but I don't have enough data to guess.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

---

First of two simultaneous responses --

There is a distinct lack of product detail here. All we know is that your parts are plated with copper, nickel and chrome. What are the thicknesses?; what is the substrate?; what type of copper is used?; what type of nickel (duplex, columnar or laminar)?; is the chrome trivalent or hexavalent? What are the field conditions for the parts? Once these details are known, someone should be able to help.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2006

---

Second of two simultaneous responses --

The spec for the plate job is of the highest automotive standard. The parts fair well in salt spray tests. Occasionally we will have a corrosion or blistering defect turn up in the field. Small green spot here and there looks to me to be caused by tiny opening through the chrome and nickel (pinhole) allowing copper oxide to escape to surface. My question is where do I start with the plater to reduce the possible occurrence of pinholes? Is it contamination in the process?

Al Gebhard

2006

---

I think what I would do is have the defective area of a defective part cross-sectioned for metallographic analysis to get a really good understanding of exactly what conditions exist at the pit or defect.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006