Metal finishing Q&As since 1989

-----

Passivation Problem

We are V Belt and High Pressure Hoses manufacturing company based at Nagpur. In house we are using end fittings for assembly. These are zinc plated and then yellow passivation is done. During assembly. of socket i.e when it is crimped (material is squeezed by almost 4 mm) the yellow passivation turns white. We need to know the process by which this problem can be overcome.In crimping process the diameter of socket reduces by 4 mm. The jaws which are crimping this socket is also metallic. Please suggest process, any consultant or any plater who can suggest solution to this problem who is in and around our place.

Ninad Darvekar
- Nagpur, Maharashtra, India
2003

---

First of two simultaneous responses --

There are certain organic materials that will react with the chromium in the yellow color and remove it. My wife's hand lotion did a wonderful job of stripping the color anywhere she touched it. It is worth investigating and testing.

James Watts
- Navarre, Florida
2003

---

Second of two simultaneous responses -- 2003

Dear Mr Darvekar,

Try to ensure the following:

1.The plating is done in Alkaline Cyanide free process.

2.The plating /passivation has had about one week of aging before you try crimping.

3. The jaws of your crimping machine do not scrape the plating. Are non metallic jaws possible? The above may minimise if not eliminate your problem.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India