-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 10647

White Rust Military Application


I have white rust forming between a Bolt/washer and a plate which are mechanically assembled. The washer is standard steel and zinc passivated IAW ASTM B633 [link by ed. to spec at TechStreet] -85, SC#, TYPE II with an Olive Drab Chromate conversion coating (military application). The plate is stainless steel made in the UK to BS 970 304S15 specs and then blackened to RA/PS 122 C. What is the white rust caused by. Will this lead to failure over time. The two parts have been in contact for only two months.

Michael Fedoruk
- Calgary, Alberta, Canada


White rust usually indicates that the zinc is corroding after the chromate conversion coating is no longer offering protection. If the olive drab coating is still visible on the outside of the washer and bolt, then I would say that the bolt and washer have become the anode in contact with the black oxided Stainless steel, and this will lead to premature failure of the coating system.

tom pullizzi monitor
Tom Pullizzi
Falls Township,


You are experiencing Galvanic corrosion. When two different types of metals come into contact, you set up a voltage and current flowing between the two metals that encourages rust. The bolt is corroding sacrificially and providing extra protection to the stainless steel. The white corrosion is zinc oxide, which is rusted plating. The next thing you will eventually see is iron oxide, which is your part's base iron rusting. Is it possible to change the design so that the bolt is made of the same stainless steel?

tim neveau
Tim Neveau
Rochester Hills, Michigan

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to 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.