-- 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 6411

Regenerating/purifying iron phosphate bath


Is there any common procedure for cleaning up an iron phosphate bath to avoid dumping it to waste periodically?

Thomas R Wallin
Illinois Environmental Protection Agency - Springfield, Illinois


My response has more to do with a philosophy and with general experience in the finishing industry, rather than specific experience purifying iron phosphating. Nonetheless, for what it's worth ...

Iron phosphate processes are usually '3-stage' processes consisting of a single bath that does triple duty of cleaning, activating and phosphatizing, followed by two rinses.

Before the days of careful attention to resource conservation, this simplicity probably made sense. But any process that does double or triple duty is a high-strung and touchy chemistry that makes you pay hell if you try to stretch its life: You need to get the dirt out, and get the organics out, and get the reduced reagents which took part in the phosphatizing reaction out, and then restore the exact pH, exact phosphate balance, etc. You may not be able to do it in a laboratory let alone a real metal finishing shop.

Frankly, I think the shop might want to give consideration to revamping the line so it has a capable alkaline pre-cleaning station followed by a neutralizing acid activation dip and then a phosphatizing step. More along the lines of a '7-stage' zinc phosphatizing process. Complicated, yes, but then you have a reasonable shot at extending the life of the tanks because you don't have to worry about maintaining phosphate balance in the pre-cleaning station, you just get the oil and dirt out; and you don't have to worry about oil and dirt in the phosphating tank.

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

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.