finishing.com -- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

HomeFAQsSuggested
Books
Help
Wanteds
Advertise
on this site
FORUM
(current
topics)
topic 4703

Reuseability of chromate rinsewater in alkaline zinc plating?


(2000)

I am working with a client who does rack alkaline zinc plating and trying to solve its excessive chemical use of its tri-chrome chromate dip. Due to increased production, their chemical usage for the chromate dip has increased significantly due to increased dragout and pH of the last alkaline zinc rinse. Because they do not want to increase rinsewater flow rate to wastewater treatment system, we are considering the counterflow of the chromate rinses back to the alkaline zinc rinse tank just before the chromate tank; the concept here is to have the acid in the rinse neutralize the alkali.

Are there any drawbacks to this concept? If so, are there easy corrections that could be made? Has anyone ever seen this kind of reuse of chromate rinsewater?

Steve Schulte
- Cincinnati, Ohio


(2000)

While this can probably be done without adverse impact on plating quality, have you asked the supplier whether a dilute nitric dip is recommended with this zinc & chromate combination? If so, that would achieve your goal while improving quality, rather than risking it.

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


(2000)

Dear Steve,

Its an interesting idea and theoretically it may work. I worry however about the adhesion of the passivation to the Zinc plating and the effects on corrosion protection . Ill try this on my shop floor too and give you a reply in a week or two. However since I only Chloride Zinc plate, I do not have the same problem as you do but I am keen on conserving water and reducing discharge.

Regards,(watch this space again)

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind supporting advertiser
Bangalore, Karnataka, India

saify logo


(2000)

Dear Steve, Tried it. Doesn't work , as it interferes with the quality of passivation. didn't get as far as the salt spray test since getting the passivation right didn't work for us. Maybe it can yet work for you. Regards,

Khozem Vahaanwala Khozem Vahaanwala
Saify Ind 
Bangalore, Karnataka, India

(2000)

Dear Mr. Schulte:

I have heard of attempts to do this, but none successful that I can remember. One problem was that precipitants were generated that settled onto the plating. They interfered with the formation of the chromate film and acted adversely in corrosion tests. Someday, perhaps, someone will come up with a technique that will render this idea practical. Sincerely, Ed Budman

ed budman
eb sig
Ed Budman
- Pennsylvania



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 Q or A 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


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.