-- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing.
    no popups, no spam
on this site
current topics

topic 0 520

Processing parts though black chromate tank on production basis


Does anyone have any ideas as to the best way to process zinc and black chromate parts through a return type automatic machine? The machine will process both black chromated and clear chromated zinc plated parts. In order to leave parts in the black chromate for the standard two minutes, the machine would have to be slowed by one-half. Is it possible to heat or make a more concentrated black chromate in order to cut the time down and still get a consistent quality finish? Any ideas as to maintaining quality control on a high production return type zinc automatic line would be greatly appreciated.


Keith Rosenblum
plating shop - St. Paul, Minnesota


Try using Missouri Electrochem's Black Chromate. It deposits in 45 seconds and is jet black. Add a little acetic acid and you get a brilliant non-rainbowing gold. Great stuff.

Good Luck,

Dave Kinghorn
Dave Kinghorn
Chemical Engineer
SUNNYvale, California



The automatic return-type plant can be programmed to have both the types of chromate passivation processes. Movement graphs for the transporters can help in adjustment of the dwell time in the black passivation station or, the pH value may be lowered to speedup the black passivation so that the dwell time can be reduced. But I feel the rinse tanks for black passivation line should be dedicated and not common. The black passivation solution should be monitored for temp, hex.chromium content and pH. The color of the black passivated zinc should not be brownish with or without iridescence. Movement of the transporters should be such as to avoid any contamination of the blue passivation by drips from the black passivation or the rinses.


Subramanian Ramajaaym
- Bangalore, Karnataka, India


Good advice on the process, Mr. Ramajaaym, thanks. But I believe that the plating machine Mr. Rosenblum is describing is not a programmed hoist/crane/transporter line. Rather, in the U.S. the phrase 'return type automatic machine' indicates either a "split rail machine" or a "side arm machine" as illustrated in the Metal Finishing Guidebook or the book Electroplated Plastics by ASEP.

And indeed, by definition, it is impossible to get an immersion in a single-station process tank that is longer than the basic dwell time. Shorter times are achievable with a delayed-set-down or advance-pick-up accessory, but longer times can only be achieved by making the chromate cell a two-station 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.