No registration, no passwords; no pop-up ads -- just aloha, fun, & authoritative answers.
As an eBay Partner & Amazon Affiliate we receive compensation for qualifying purchases.
Home /
Search 🔍
the Site
pub  Where the world gathers for
plating, anodizing, & finishing Q&As since 1989


Technical query regarding phosphating


We do Zinc phosphating on carbon steel valve bodies before painting. The external surface of the bodies are then painted after assembly and the internal surfaces of the valve bodies are oiled for rust prevention.

As these valves go into process industries where a variety of fluids are handled by these valves, I want to know whether the zinc phosphate coating will react with any of the process fluids ?

Should we check for compatibility of Zn Phosphate coating with the type of fluid used ?

mahesh malkarnekar
engineers. - India


From your letter it is understand that the oil is not remain in the inlet part of the valve .

Zinc Phosphate layer will not survive in the following solutions:

A.Strong acids like Hydrochloric Acid , Sulfuric Acid , Nitric Acid and so on .

B.Strong Alkaline solution containing more then 10 grams per liter Sodium Hydroxide or Potassium Hydroxide.

High temperature solution will accelerate the phosphate removal and even weaker acids like organic acids will destroy the Zinc Phosphate (Worth checking before application) the same is for weaker Alkaline solutions containing Sodium Carbonate.

yehuda blau
Yehuda Blau
YB Plating Engineering and Quality - Haifa Israel

(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:

Chemicals &
Consult'g, Train'g
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"