Metal finishing Q&As since 1989

-----

At Equal Thicknesses, is Hot Dipped Galvanizing Better than Electroplated Zinc

I have an application that is currently galvanized. We are experiencing adhesion problems related to the coating during a subsequent molding operation. We have also encountered flaking which compromises the quality of the finished part. I would like to change to a different coating and electroplated zinc is easier to bond to during molding. However, I am getting resistance because of the perception that the hot dip galvanizing gives better protection from corrosion.

Edine Heinig
End user, product designer - Pewaukee, Wisconsin
2007

---

2007

It is very unusual for electroplating thicknesses to even approach galvanizing thicknesses, so there probably isn't a whole lot of substantiated field data on the subject, Edine. Instead we have platers sometimes saying "zinc is zinc" and galvanizers talking of intermetallics improving the electrochemical potential and slowing the corrosion.

But the practical answer for you then (assuming the adhesion problem with galvanizing is unsolvable) is to electroplate with a zinc alloy such as zinc-iron, zinc-nickel, or zinc-cobalt because in this case the electrochemical potential is carefully engineered to be optimal and the claim that galvanizing is better thickness-for-thickness would not have grounds.

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