-- The Home Page of the Finishing Industry
Serious Education & the most FUN
you can have in metal finishing smiley

No popups, spam, registration or passwords
on this site
current topics
topic 6037

Golden Color of Zinc Electroplating Fades on Castings


I am doing electroplating of zinc on sg 420/12 castings of around 1 kg.

1. I need complete theory of electroplating and specially for zinc electroplating.

2. I dip the pieces in golden passivation but the golden color is not very stable and it changes or fades after a few weeks or months.What can I do to avoid this.

Faisal Mansoor Khan
Rastgar Engg company. - Islamabad, Pakistan


Hello Faisal.

Successful industrial electroplating is pretty complicated, so we are happy to try to address individual questions but unfortunately no one can give you the complete theory of zinc electroplating in a few paragraphs. There are whole books written just on zinc plating, such as "Zinc Plating" [link is to product info at Amazon], but a reasonably available book that might be a starting point for your studies is the Metal Finishing Guidebook. You can see our "must-have book list" for additional suggestions. As your run into specific problems please get back to us with details.

Proprietary chromates are commercially available that are formulated to deliver a more stable color than generic mixes, so that would be one avenue to explore. Best of luck.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Your part is most likely porous. The parts are exposed to the plating chemistry longer than any other process and if the parts are porous they will absorb plating solution into the pores of the part.The Plating chemistry which the part sees for approx. 20 minutes is leaching your chromate.

Things to try: Take a casting (part) and after plating rinse it in boiling water for 60 seconds. then rinse in cold water. repeat 2 more times and Chromate the part with your yellow (gold) chromate rinse and dry.

If this reduces the color fading or bleed out the problem is in the porosity of the casting. The parts may need to be sealed prior to plating. The sealing process is quite involved. I believe Loctite sells the chemistry, but it requires special equipment.

danny tynes
Danny Tynes
used electroplating equipment
- Birmingham, Alabama

If you have a question in mind which seems off topic, please Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.