The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Nickel underplating thickness

 

Dear Sir,

What is the optimum nickel plating thickness over phosphorous bronze?

I have read some articles about the nickel under-plating. However, one of them claim that the nickel thickness should be around 2.5 - 5.0 micro-meter.

On the other hand, one actually claim that it performs best at a thickness of approximately 50 micro-inches (which is equivalent to 1.27 micro-meter), regardless of the thickness of the gold. He also mentioned that additional thickness of nickel could be detrimental as it increases the roughness of the surface due to the decreased wear resistance.

We understand that the gold over nickel is a dominant plating technology in Asia. Hence, our Company is also using this type of coating for our motor parts (phosphorous bronze). However, the surface finish is quite rough and we are still trying to improve the surface smoothness.

Therefore, I am in dilemma, as I did not really know which thickness is more relevant to my situation. Currently, our company is using a nickel plating thickness of 2 ~ 4 micro-meter. I hope you can enlighten me regarding this question. Thanks.

With Best Regards,

Lau Shir Ling
- Singapore

---

 

What is the optimum nickel plating thickness over phosphorous bronze? What is the application? Marine hardware, electrical contact, etc.

I have read some articles about the nickel under-plating. However, one of them claim that the nickel thickness should be around 2.5 - 5.0 micro-meter. That sounds like 0.0001 to 0.0002 inches, which is little more than a strike plate, it may be enough for a barrier to copper diffusion.

On the other hand, one actually claim that it performs best at a thickness of approximately 50 micro-inches (which is equivalent to 1.27 micro-meter), regardless of the thickness of the gold. He also mentioned that additional thickness of nickel could be detrimental as it increases the roughness of the surface due to the decreased wear resistance.

You can plate 0.002 inches of bright nickel and still have a smooth plate, but you need good filtration and a properly balanced bath. I don't know what you mean by decreased wear resistance. Plating deposits of columnar structure tend to get rougher as the thickness increases, so this may be what is happening in your case.

  
Tom Pullizzi
Falls Township, Pennsylvania

---

---

Q. We are doing plating of brass cases with nickel base coat by electroplating process followed by titanium nitride and flash gold by PVD Route. On usage pitting corrosion noticed on brass components within a short period. What is the minimum thickness of nickel is required to avoid this corrosion ? Or any other under coat is required to protect brass ?

Ramasubramanian Sankarabhatter
- Bangalore, Karnataka, India
January 29, 2013

---

---

Q. Dear Mooney,
Thanks for your reply.
Why do you recommend white bronze as a base coat before nickel?
Is it OK if I do copper undercoat instead of white bronze?
Any other metallic coating is applicable to reduce corrosion?

Ramasubramanian

Ramasubramanian Sankarabhatter
- Bangalore, Karnataka, India
February 14, 2013

---