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

Zinc plating problems in case-carburized component

February 6, 2010

Hi,

I request your assistance. We are plating an externally threaded case carburized component, which despite the heat-treaters efforts has scale. This component looks like a disc (the Outer Dia is 40 mm & the thickness is 13 mm).

• When we do light abrasive cleaning to remove the scale, the plating quality (visually) is not good. There are many black spots on the face of the component
• When we do heavier abrasive cleaning, we notice some damage to the external thread -- the plating is OK but about 50% of components do not answer the thread GO gauge.
• We tried shot-blasting with glass beads but this also produces thread damage. Likewise sand blasting also produces thread damage

Due to case hardening, the thin cross-section of external threads are very hard & somewhat brittle.

Should we zinc phosphate as a pre-treatment for zinc plating? (I don't even mind the extra cost of this, if we can be assured of good quality). Or would you have any other suggestions

I would much appreciate your recommendations on how to deal with this problem. Thanks!

Anup Sagar
Product Engineer - Chennai, India

---

February 10, 2010

Dear Anup Sagar,

if the part is for Asthetic reason, Zinc plating will not give 100% Guarantee. May be you need to think of powder coating.

Still you are not able to change the Zinc plating.
Before plating do the Alumina blasting and try for Zinc plating or before your Polishing do the Descaling process.

Kannan Boopathi
- Salem, Tamil Nadu, Salem