Hobbyists & Industry luminaries alike learn on every visit
(we earn from 'affiliate link' purchases)

Curated with aloha by
Ted Mooney, P.E. RET

finishing.com -- The Home Page of the Finishing Industry

  The authoritative public forum
  for Metal Finishing 1989-2025

-----

Clear Chromate on zinc plating is turning yellow

Hi. I have a zinc product, plated with a clear chromate conversion coating. My problem is that after we ship to the customer about 50% are turning yellow after a few days. The problem only occurs after they are put in their final packaging which is a Bio Bag? Any ideas what might be causing it?

Darragh Murphy
engineer - Cork, Ireland
October 20, 2011

October 24, 2011

This is a known problem which is mainly observed on big parts.

Try to reduce the conversion coating's thickness by reducing dipping time, pH and concentration.

Sara Michaeli
Tel-Aviv-Yafo, Israel

November 27, 2011

Yes, I agree with Miss Sarah,
This type of yellow shades are more found on the bigger surface area parts...even if you control your pH, concentration etc. with huge volume now a days it is much more difficult to control and get a pure clear white finish on bigger parts especially on zinc trivalent white passivation.

Jayakumar Selvaraj
metal finisher - Chennai, Tamilnadu, India

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully 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 might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: