Determination of the Composition of Chrome Plating BathsK. Andrzejewski1,2*, Y.E. Oh1,2*, J. Podell1,2*, M. Lieberman1;

1University of Notre Dame, Notre Dame, Indiana 46556; 2Marian High School, Mishawaka, Indiana 46544BACKGROUND:

An American Chrome Plating Company (name withheld by request) performs chrome plating on work rolls which are used in the steel and aluminum industries to flatten metal sheeting. The work puts great wear and tear on the rolls, so replating must be performed frequently (every 2-4 days). With a focus on making the company’s practices more ‘green’, it is important to maintain optimal concentrations of chemicals (in particular, chromium) in the plating baths. It is also important to minimize hazardous waste products for both ecological and economic reasons. There are several American locations for the company, labeled as Plants 1 through 5. (No samples were available from Plant 5; Plant 1 has two separate plating tanks –A and B; Plant 4 has two plating tank cells – A and B.) Each plant has a wash or soak tank where the rolls are processed before and/or after plating. Potentially hazardous materials collect in these tanks.

Figure 1. Newly plated work roll.

Figure 3. Plating Bath Samples taken from the tanks 1A and 1B.

GOALS:1) Analyze and determine the major elements composing the 6 different plating baths.2) Determine density of plating baths to devise a possible method for detecting composition changes.3) Analyze and determine composition of wash tanks to determine hazardous components.4) Determine possible methods to reduce the amounts of hazardous materials, or to reduce the level of hazard.

Figure 2. Work roll about to be inserted in Plant 1A plating bath

ACKNOWLEDGEMENTS:

Dr. Doug Miller, Jordan Hall of Science, Notre Dame, IN

Kaneb Center RET Program, Notre Dame, IN

Center for Environmental Science and Technology (CEST), Notre Dame, IN

Jon Loftus, Research Technician, CEST, Notre Dame, IN

REFERENCES

CHROMIUM CONTENTChromium content of the samples was determined by ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometry). In this process, a sample is nebulized to micro-droplet particles which are passed through an extremely hot plasma stream. Particles are excited, releasing electrons, which return and emit light. Emission spectra are determined to identify specified elements. Figures 4 and 5 show chromium concentrations in ppm from ICP-OES examination.

Figure 4. ICP Concentration Results for the Plating Tanks

Plant 1 A Plant 1 B Plant 2 Plant 3 Plant 4 A Plant 4 B Plant 5

g/mL 1.14857 1.16968 1.20402 1.22225 1.18307 1.18740 Sample has not arrived

DENSITYDensity of each sample was determined with the intention of developing an efficient chromium

concentration indicator. This investigation is yet to be pursued.

Figure 10. Initial Average Densities of the Plant Plating Baths (from 10 mL aliquots)

l

Figure 11 shows the density of the daily samples from the Plant 1 A tank. They were calculated to determine the effect of adding the chromic acid flake to the bath.

Element λ Plant 1 A Plant 1 B Plant 2 Plant 3 Plant 4 A Plant 4 B

Cr 267.716 105700 131900 153200 144200 121300 120100Cr 205.560 106200 132700 154400 145300 122100 120700Cr 284.325 106000 132200 153400 144700 121900 120800Cr 357.869 105000 129600 149000 141900 120600 119500

Average 105725 131600 152500 144025 121475 120275Std. Dev. 525.1984 1373.56 2391.652 1486.327 675.1543 602.0797

Monday 7-6-09

Tuesday 7-7-09

Wednesday 7-8-09

Thursday 7-9-09

Friday 7-10-091.131.141.151.161.171.181.19

1.2 Figure 11. Average Density of Daily Samples

Den

sity

(g/m

L)

Addition of 300 lbs. of chromic acid flake

0 1 2 3 4 5 60

50000

100000

150000

200000

250000

300000

Plant 1 A Plant 1 B

Plant 2Plant 3 Plant 4 A

Plant 4 B

Figure 6. Plating Bath Chromium Concentrations at λ 267.716 nm

Concentration (ppm)

Inte

nsity Plant 1 A = 1.057ppm

Plant 1 B = 1.319ppmPlant 2 = 1.532ppmPlant 3 = 1.442ppmPlant 4 A = 1.213ppmPlant 4 B= 1.201ppm

Monday 7-6-09

Tuesday 7

-7-09

Wednesd

ay7-8-09

Thursday7

-9-09

Friday7

-10-090

2

4

6

8

10

12Figure 7. Progression of Chromium Concentra-

tions of Daily Samples

Cr 267.716

Conc

entr

ation

(mg/

L)

Addition of 300 lbs. of chromic acid flake

WASH TANKFigure 6 represents the concentration of chromium in a 1:100,000 dilution at the wavelength 267.716 nm for the different Plating Tanks. The 10.0805ppm standard was left off to show the sample data points more clearly.

Figure 7 illustrates the concentration of chromium in the Plant 1 A Tank at the wavelength 267.716 nm during the progression of one week. After the sample was taken on Wednesday, 300 lbs. of chromic acid flake was added to the tank.

0 5 10 15 20 250

0.5

1

1.5

2

2.5

Plant 1

Plant 3

Plants 2 and 4

Figure 12. Wash Tank Samples vs. Starch Indicator Standards

Starch Indi-cator Stan-dards

Cr Concentrations (ppm)

Abso

rban

ce a

t 540

Figure 12 demonstrates the concentrations of chromium in the wash tank samples as determined through a starch indicator/iodine test measured by UV-Vis.

Figure 13. Plant 1 A wash tank

Figure 14. Wash tank waste sample from Plant 1 A

Norseth, T. “The Carcinogenicity of Chromium and Its Salts.” Editorial. British Journal of Industrial Medicine. 9 October 1986: 649-651.

Zaki, Nabil. “Chromium Plating.” Product Finishing Magazine. 6 January 2000: 1-10.

Chromium8%

Water83%

Sulfate and other metal ions

9%

Figure 8. Wednesday 7-8-09 Chromium

11%

Water80%

Sulfate and other metal ions

9%

Figure 9. Friday 7-10-09

Figure 16. Wall of the Wash Tank

Element % ±

Fe 89.6 2.14

Co 6.55 0.78

Pb 3.36 0.48

Mo 0.49 0.1

Figure 15. Wash Tank Solids

Element % ±Fe 58.92 1.56Cr 19.92 1.04Pb 16.17 0.54

Mo 4.17 0.18

Zr 1.45 0.1

Figures 8 and 9 represent the change in percentages of the sample content before and after the addition of chromic acid.

Figures 15 and 16 show the x-ray

fluorimeter (XRF) data for percentage of metal ions from

wash tank materials.

The wash tank is used to rinse, soak, clean and prepare rolls for plating, as well as a catch bin for grinding the rolls in some plants. Samples from four plants were tested for hexavalent chromium using an iodine/starch indicator test, with color changes determined by UV-Vis.

The water in the Plant 1 A tank is continuously collected and periodically siphoned off at great expense due to hazardous waste content. The walls of the tank are coated with an accumulation of solid material that remains behind. X-Ray Fluorimetry (XRF) was used to determine the makeup of the metallic solid, as well as the tank wall itself.

CONCLUSIONS AND FUTURE PLANS

All studies thus far have been preliminary investigations and further experimentation and repetition is necessary. Throughout the following year, plans hope to address the following:

•Further examination of non-chromium content of plating baths via ICP-OES.

•Repetition of chromium studies via ICP-OES.

•Repetition of daily sample procedures. •Separation and dilution of the four wash tank samples and ICP-OES determination of the composition.

•Examination of possible methods to reduce wash tank hazards.

•Exploration of methods to monitor chrome plating bath contents via density.

Cr Standard

Plant 1 A Plant 1 B Plant 2 Plant 3 Plant 4 A Plant 4 B0

20000

40000

60000

80000

100000

120000

140000

160000

180000Figure 5. Average Chromium Concentrations

Sample

Conc

entr

ation

(mg/

L)