INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 159

1.   Headline:  Replacement of Hexavalent Chromium with
     Trivalent Chromium in Decorative Chrome Plating Reduces
     Sludge Generation

2.   Background:  See below.

3.   Cleaner Production Application:  Material substitution

4.   Description of Cleaner Production Application:  Cleaner
     production is achieved by plating with trivalent rather
     than hexavalent chromium.  The tendency of trivalent
     chromium to be oxidized to hexavalent chromium was
     overcome by using a special membrane surrounding the
     anodes.  This also allows use of anodes made of lead.  The
     low deposition rates associated with trivalent chrome
     plating were grossly increased by using specially
     developed in-house organic additives to modify the
     reactions and give performances superior to the
     traditional process.  This results in production which is
     20-40% higher.

     Case Study Summary

     Process and Waste Information:  Although the composition
     of the plating line was not clear from the source
     document, it is assumed that the sequence consists of
     bright nickel plating with drag-out recovery, two clean
     running rinses, chrome plate, two additional rinses, and a
     final hot rinse.  In the traditional process, hexavalent
     concentrations are sometimes as high as 120 g/l.
     Trivalent chromium replaces hexavalent chromium in the new
     process and organic compounds are added.  This results in
     a decrease in sludge generation of over 95%, energy
     consumption reduced by over 50%, lower current densities,
     no chloride in the electrolyte, and a 98% reduction in
     waste treatment costs.  No reduction chemicals are needed
     with the new process.  Product quality was greatly
     improved due to better coverage and more uniform plating.

     Stage of Development:  The technology has been fully
     implemented and in operation since about 1985.

     Level of Commercialization:  It appears the company has
     developed the procedure and sells it under the name
     "Envirochrome-90".  The membranes were developed for
     mercury-free electrolysis of sodium chloride.  Canning is
     a supplier of machineries to the electroplating industry.

     Material/Energy Balances and Substitutions:

Material Category         Quantity Before*            Quantity
After*

     Waste generation:               100%
     95%
    Feedstock use:                  N/A
N/A
    Water use:                      N/A
N/A
    Energy use:
     Consumption                     100%
     50%
Current densities         10-15Amp/dm2
3.2-8Amp/dm2         8-12V

    *Exact quantities were not supplied.

5.   Economics*

     Investment Costs:  Actual figures on investments are not
     given, and these estimates may be low.  A comparison is
     made on the investment costs for a traditional plating
     line and the new plating process for a plant producing 3
     million nickel and chrome plated water fittings per year.

                                Traditional Technology
                    New Technology

Plating plant               175,000
135,000
Effluent plant              70,000
52,000

     Operational & Maintenance:  Only costs for water treatment
     were given for the traditional and new  technologies as
     follows:

                                Traditional Technology
                    New Technology

Chrome reduction                      6,459
                              0
Hydroxide precip.                     1,605
                              120
Sludge disposal                       2,905
                              130
Labor and materials                   2,050
                              50

Total                              13,064
                    300


     *No costs were given for labor, maintenance of membranes,
     or energy consumption for other operations.  Membrane life
     is assumed to be indefinite since no signs of wear
     occurred after five years of operation.

     Payback Time:  It is not possible to calculate a payback
     time due to lack of data but appears the technology is
     relatively cheap compared to the traditional technology.

6.   Advantages

     Sludge production decreased by 95%, waste treatment costs
     decreased by 98%, and power consumption decreased by over
     50%.  Electrical current densities are lower and the
     electrolyte is less corrosive since no chloride is
     present.  The technology appears to be cheaper than the
     traditional process and results in improved product
     quality.

     Benefits from improved public relations, reduced
     liabilities, and changes in regulatory compliance were not
     discussed.

7.   Constraints:  The brownish color of trivalent chrome may
     be a problem for some people.

8.   Contact:  Contacts and Citation

     Type of Source Material:

     Document 1:  UNEP report
     Document 2:  British government leaflet
     Document 3:  Plant leaflet

               Citation:Document 1: Title not given.
     B. Johnson, W. Canning Materials Ltd.
     P.O.Box 288, Great Hampton Street
    Birmingham B18 6AS, UK.
    TEL 44-21-236-8621
    FAX 44-21-236-0444

     Document 2: Clean Technology.
     EPT Office, Department of the Environment
     Room B 357, Romney House
    43 Marsham Street
    London SW1P 3PY, UK
    TEL: 4421-276-8318

     Document 3: Envirochrome Process Operating Guide
     W. Canning Materials Ltd.
     P.O. Box 288
     Great Hampton Street
     Birmingham B18 6AS, UK
    TEL: 44 21-236-8621
     FAX: 44 21-236-0444.

9.   Keywords:  United Kingdom, UK, electroplating, material
     substitution, ISIC 3471, chrome, trivalent chromium,
     hexavalent chromium, rinsing, sludge, plating,
     electrolysis.

10.  Reviewer's Comments:  This case study was originally
     compiled by the UNEP IE Working Group on Metal Finishing.
     It underwent a UNEP IE funded technical review in 1994 for
     quality and completeness.  It was edited for the ICPIC
     diskette in July 1995.

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