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

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.


Related in: MedlinePlus

Total mass gain (μg cm−2) and corresponding conditions as a function of pH of the scratched iron roof materials after 60 days of exposure.
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fig5: Total mass gain (μg cm−2) and corresponding conditions as a function of pH of the scratched iron roof materials after 60 days of exposure.

Mentions: Stress cracks and physical scratches can play a significant role in the corrosion behavior of materials [36]. When the outer protective layer of a surface is cracked or scratched, the inner layer of the material is exposed to the atmosphere. Such cracks or scratches can occur during manufacturing, transportation, or service not only by chemical means but also by friction with local materials including particulate matters, trees, and its falling parts. The latter is particularly important as it is very common to observe big shade trees near buildings and houses in Ethiopia. Thus, we considered exposure of new but scratched iron materials to corrosive synthetic air under simulated atmospheric conditions and compared their corrosion rates with those without any surface scratches or cracks. Similar five groups of sample materials described in the above sections were considered except, in this case, the surface which is physically scratched with stainless steel before being subjected to the laboratory exposure. The results of the laboratory exposure of scratched iron materials and control samples to synthetic corrosive air under different atmospheric conditions are shown in Figure 5. Comparing the results of Figures 5 and 4, a significant effect of surface scratches on the corrosion rate was observed with all other effects appearing as presented in Figure 4. Our results point to the importance of avoiding surface scratches during manufacturing, packaging, and transporting of corrugated iron roof materials.


Spectrophotometric Method for the Determination of Atmospheric Cr Pollution as a Factor to Accelerated Corrosion
Total mass gain (μg cm−2) and corresponding conditions as a function of pH of the scratched iron roof materials after 60 days of exposure.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Total mass gain (μg cm−2) and corresponding conditions as a function of pH of the scratched iron roof materials after 60 days of exposure.
Mentions: Stress cracks and physical scratches can play a significant role in the corrosion behavior of materials [36]. When the outer protective layer of a surface is cracked or scratched, the inner layer of the material is exposed to the atmosphere. Such cracks or scratches can occur during manufacturing, transportation, or service not only by chemical means but also by friction with local materials including particulate matters, trees, and its falling parts. The latter is particularly important as it is very common to observe big shade trees near buildings and houses in Ethiopia. Thus, we considered exposure of new but scratched iron materials to corrosive synthetic air under simulated atmospheric conditions and compared their corrosion rates with those without any surface scratches or cracks. Similar five groups of sample materials described in the above sections were considered except, in this case, the surface which is physically scratched with stainless steel before being subjected to the laboratory exposure. The results of the laboratory exposure of scratched iron materials and control samples to synthetic corrosive air under different atmospheric conditions are shown in Figure 5. Comparing the results of Figures 5 and 4, a significant effect of surface scratches on the corrosion rate was observed with all other effects appearing as presented in Figure 4. Our results point to the importance of avoiding surface scratches during manufacturing, packaging, and transporting of corrugated iron roof materials.

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.


Related in: MedlinePlus