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Spectrophotometric Method for the Determination of Atmospheric Cr Pollution as a Factor to Accelerated Corrosion

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ABSTRACT

The effect of Cr(VI) pollution on the corrosion rate of corrugated iron roof samples collected from tanning industry areas was investigated through simulated laboratory exposure and spectrophotometric detection of Cr(III) deposit as a product of the reaction. The total level of Cr detected in the samples ranged from 113.892 ± 0.17 ppm to 53.05 ± 0.243 ppm and showed increasing trend as sampling sites get closer to the tannery and in the direction of tannery effluent stream. The laboratory exposure of a newly manufactured material to a simulated condition showed a relatively faster corrosion rate in the presence of Cr(VI) with concomitant deposition of Cr(III) under pH control. A significant (P = 0.05) increase in the corrosion rate was also recorded when exposing scratched or stress cracked samples. A coupled redox process where Cr(VI) is reduced to a stable, immobile, and insoluble Cr(III) accompanying corrosion of the iron is proposed as a possible mechanism leading to the elevated deposition of the latter on the materials. In conclusion, the increased deposits of Cr detected in the corrugated iron roof samples collected from tanning industry zones suggested possible atmospheric Cr pollution as a factor to the accelerated corrosion of the materials.

No MeSH data available.


The levels of total Cr(III) corrected for blank (new material) detected in exposed samples against distance from the tannery.
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fig1: The levels of total Cr(III) corrected for blank (new material) detected in exposed samples against distance from the tannery.

Mentions: Chromium is naturally present in corrugated iron roof as component of the steel alloy. But this natural level is expected to increase with Fe coupled atmospheric transformation of the hexavalent Cr into the trivalent Cr in areas where industrial activities can lead to atmospheric pollution by Cr(VI). We determined total Cr levels as well as the levels of major species (Cr(III) and Cr(VI)) from speciation experiments in three different groups of the roofing material. The levels of total Cr corrected for blank (new material) detected in exposed samples against distance from the tannery are presented in Figure 1. The levels of total Cr detected in the damaged materials ranged from 113.892 ± 0.17 ppm to 53.05 ± 0.243 ppm. The levels showed a decreasing trend with distance from the tannery. The mean concentrations of Cr in new corrugated iron samples purchased from four shops and that of four control samples collected at 100, 200, 300, and 400 km distances farther from the tannery were 8.5 ± 0.045 and 9.66 ± 0.704 ppm, respectively. The maximum levels of Cr detected in new and control samples were 8.908 and 10.433 ppm, respectively, which is still lower than the minimum level detected in exposed and damaged samples. No significant differences (P = 0.05) among the levels of Cr in control samples collected at different distances (100 km and above) were detected. Similarly the levels of Cr in the new corrugated iron materials purchased from four shops did not show significant (P = 0.05) differences.


Spectrophotometric Method for the Determination of Atmospheric Cr Pollution as a Factor to Accelerated Corrosion
The levels of total Cr(III) corrected for blank (new material) detected in exposed samples against distance from the tannery.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5392392&req=5

fig1: The levels of total Cr(III) corrected for blank (new material) detected in exposed samples against distance from the tannery.
Mentions: Chromium is naturally present in corrugated iron roof as component of the steel alloy. But this natural level is expected to increase with Fe coupled atmospheric transformation of the hexavalent Cr into the trivalent Cr in areas where industrial activities can lead to atmospheric pollution by Cr(VI). We determined total Cr levels as well as the levels of major species (Cr(III) and Cr(VI)) from speciation experiments in three different groups of the roofing material. The levels of total Cr corrected for blank (new material) detected in exposed samples against distance from the tannery are presented in Figure 1. The levels of total Cr detected in the damaged materials ranged from 113.892 ± 0.17 ppm to 53.05 ± 0.243 ppm. The levels showed a decreasing trend with distance from the tannery. The mean concentrations of Cr in new corrugated iron samples purchased from four shops and that of four control samples collected at 100, 200, 300, and 400 km distances farther from the tannery were 8.5 ± 0.045 and 9.66 ± 0.704 ppm, respectively. The maximum levels of Cr detected in new and control samples were 8.908 and 10.433 ppm, respectively, which is still lower than the minimum level detected in exposed and damaged samples. No significant differences (P = 0.05) among the levels of Cr in control samples collected at different distances (100 km and above) were detected. Similarly the levels of Cr in the new corrugated iron materials purchased from four shops did not show significant (P = 0.05) differences.

View Article: PubMed Central - PubMed

ABSTRACT

The effect of Cr(VI) pollution on the corrosion rate of corrugated iron roof samples collected from tanning industry areas was investigated through simulated laboratory exposure and spectrophotometric detection of Cr(III) deposit as a product of the reaction. The total level of Cr detected in the samples ranged from 113.892 ± 0.17 ppm to 53.05 ± 0.243 ppm and showed increasing trend as sampling sites get closer to the tannery and in the direction of tannery effluent stream. The laboratory exposure of a newly manufactured material to a simulated condition showed a relatively faster corrosion rate in the presence of Cr(VI) with concomitant deposition of Cr(III) under pH control. A significant (P = 0.05) increase in the corrosion rate was also recorded when exposing scratched or stress cracked samples. A coupled redox process where Cr(VI) is reduced to a stable, immobile, and insoluble Cr(III) accompanying corrosion of the iron is proposed as a possible mechanism leading to the elevated deposition of the latter on the materials. In conclusion, the increased deposits of Cr detected in the corrugated iron roof samples collected from tanning industry zones suggested possible atmospheric Cr pollution as a factor to the accelerated corrosion of the materials.

No MeSH data available.