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  for Metal Finishing since 1989
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Hot dip galvanizing pollution prevention

2002

Dear Finishing.com

I am interested in new treatment technologies and water reduction methods currently being used in the hot dip galvanization process.

We are assisting an eastern European Galvanizer investigating improved operating procedures, promoting sound environmental practices. Our goals are to assess and identify opportunities for water conservation and pollution prevention (P2), and to identify new technologies used by American galvanizes.

I have surveyed the following P2 ideas for the facility and could use additional information or reference sources for some of the more involved ideas;

Double dipping in rinse water after pickling.
Predip into rinse before pickling (dragin/dragout)
Counterflow on all rinse tanks
Conductivity controls for rinse
Extend drain time
Top sprayers
Master solenoid plus flow restrictors, Low flow rinse nozzles
Separate rinse waste streams (pickling, degreasing from flux)
Lids on tanks to reduce evaporation
Create an everlasting pickling bath (remove oil and Fe from bath)
Oxidize excess Fe in preflux solution
Use of cleaner rinse water (increase productivity?)
More analytical testing to match closer needs of NH4Cl. Reduce waste
Acid recovery from rinse waste stream
Biodegreasers
Discontinue NH4Cl in flux, use ZnCl2

I am looking for ideas which have had the greatest success in the hot dip industry, and information about amazinc and Picklex® [affil links]. If you could make suggestions and additions, your help or guidance would be appreciated.

Thank you,

Bo B [surname deleted for privacy by Editor]
engineering - Lafayette, California, USA

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The first seven look like they came from my old booklet "20 Ways to Cut Water Usage in Plating Shops", Bo, so I'll be happy to clarify if anything was unclear, and leave the rest for another reader.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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Bo,

Almost all the techniques you mention are, for an insider, standard techniques. Without these, a pretreatment plant (whether it is for hot-dip zinc or not) here in Europe is unimaginable. But ... it is impossible to say which of these techniques "is the best". To find out in what combination they would be suitable for a specific plant has to be calculated and engineered by someone who knows about the subject. Therefore I suggest don't invent the wheel again, but consult an expert, preferably one of the consultants you find in the consultants section of this site.

Remmelt Bosklopper
- Enschede, The Netherlands
2002