The authoritative public forum
  for Metal Finishing since 1989
  

  -----

How to tint galvanizing to the color of cadmium

1998

Dear Sirs,

I am trying to run galvanized hard drawn through a spring coiler and the galvanized coating is giving me a nice shiny appearance. What I need it to be able to tint the material a color similar to cadmium plate AMSQQP416 type II. If we can accomplish this with a coating that would be great. We also run this spring through a conveyor oven at 350 degrees. If there is a coating that can be applied to the wire before forming that then would turn a golden yellow upon heat..that would be acceptable. We are open to any additional ideas

Robert Guard

---

Cadmium is the same silvery color as zinc. The golden yellow you are describing is due to a yellow chromate conversion coating, which can be applied to zinc as well as cadmium. But the problem is that it loses its protective value, and can dehydrate and slough off starting at about 150 °F. After baking at 350 °F it would have lost most of its value, although it might indeed be the color you are seeking. If it would be acceptable to chromate the finished parts after baking, I think you could get the color match you are looking for, and corrosion resistance as well.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1997

---

I agree, deposit the conversion coating after heat treatment or it will turn a dirty deep brown. It may also not make it through the coiler in-tact. The best coatings are the old Allied Kelite line, now owned by Macdermid. Every color in the rainbow is available, though the non-standard ones are organic based.
good luck,

Dave,
SUNNYvale, CA

Dave Kinghorn
Chemical Engineer
SUNNYvale, California
1997