The authoritative public forum
  for Metal Finishing since 1989
-----

Clear zinc chromate finish on cast iron

I have an iron sand casting that has some extensive machining done to it. After the maching was complete, it was sent out for a clear zinc chromate finish. The part came back and the machined surfaces were extremely rough, almost like sandpaper. Is clear zinc chromate the correct finish to use for corrosion protection? What caused the finish to become so rough? Is there something special that must be done to cast iron to prevent this roughness? Any help with this problem would be appreciated. The part is approximately 10 inches by 5 inches and 1 inch thick.

James A. Micket
- Rochester, New York
2005

---

You can try to improve the base metal finish by giving sand blasting. Regarding the corrosion protection, clear chromate will give lower sst life. If you are under ELV regulation then trivalent chromate over zinc cobalt alloy will give sst life of 120 plus hour.

P. Gurumoorthi
electroplating process chemicals - Chennai, Tamilnadu, India
2005