PEOPLE helping each other -- No AI, no cost, no reg'n, no damn popups
(As an Amazon Associate & eBay Partner we earn from qualifying 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

-----

ASSURING STEEL IS UNPASSIVATED

2003

1. I AM USING GALVANIZED STEEL, I WANT TO TAKE OFF THE PASSIVATION, WHAT PRODUCT SHOULD I USE?

2. IS THERE A TESTING METHOD TO MAKE SURE THE METAL IS UN-PASSIVATED?

THANK YOU,

SERGE DORE
- GRANBY, QUEBEC, CANADA

2003

The meaning of the word "passivation" is very tricky in this instance. Generally the term "passivation" is applied to stainless steels, and refers to the building of a chrome-rich surface skin. The term "passivation" is also sometimes used, however, to refer to the chromate conversion coating that is applied to zinc plated and zinc galvanized surfaces. But the way you are using the term, it seems like you are really asking how to remove the zinc, not just the chromate?

The zinc will almost instantly dissolve in hydrochloric acid; in fact the reaction can be violent.

If you are trying to remove just the chromate conversion coating, I think scrubbing it with trisodium phosphate ⇦ this on eBay or Amazon [affil links] and pumice ⇦ this on eBay or Amazon [affil links] will do it. There are ASTM standard "spot tests" for the presence of the chromate.

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

(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: