• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.396-401
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• 1995

Epoxy coated reinforcing steels (ECRs) were acquired from ten sources and coatings from each source were initially characterized in terms of defects, thickness, solvent extraction weight loss and hardness. Testing involved exposure in three aqueous solutions at elevated temperature (8$0^{\circ}C$) and in chloride-contaminated concrete slabs under outdoor exposure, It was found that the density and size of coating defects was the promary factor affecting ECR performance. The equivalent circuit analysis using electrochemical impedance spectroscopy (EIS) data indicated that the impedance response for well-performing ECR specimens showed no signs of active degradation at the interface although diffusional processes similar to those noted for poorly performing bars occurred here. Experimental results also indicated a relationship between corrosion behavior and bar source. Weight loss upon solvent extraction correlated with impedance reduction from hot water exposure. Coating defects during most of the tests, especially in high pH solutions containing chloride ions. ECRs with excessive coating defects, either initially present or ones which developed in service, performed poorly in every test category regardless of source. Forms of coating failure were extensive rusting at defects, blistering, wet adhesion loss, cathodic delamination, underfilm corrosion and coating cracks. These occurred sequentially or concurrently, depending on the condition of the ECR and nature of the environment

• Journal of Soil and Groundwater Environment
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• v.16 no.2
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• pp.12-29
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• 2011

Risk-based screening levels (RBSLs) of some pollutants for residential adults were derived with risk assessment tools developed by United States Environmental Protection Agency (USEPA), American Society for Testing and Materials (ASTM), and Korea Ministry of Environment (KMOE) and compared each other. To make the comparison simple, ingestion of soil, dermal contact with soil, outdoor inhalation of vapors, indoor inhalation of vapors, and inhalation of soil particulates were chosen as exposure pathways. The results showed that the derived RBSLs varied for every exposure pathway. For direct exposure pathways (i.e., ingestion of soil and dermal contact with soil), the derived RBSLs varied mainly due to the different default values for exposure factors and toxicity data. When identical default values for the parameters were used, the same RBSLs could be derived regardless of the assessment tools used. For inhalation of vapors and inhalation of soil particulates, however, different analysis methods for cross-media transfer rates were used and different assumptions were established for each tool, identical RBSLs could not be obtained even if the same default values for exposure factors were used. Especially for inhalation of soil particulates pathway, screening level derived using KMOE approach (most conservative) was approximately 5000~10000 times lower than the screening level derived using ASTM approach (least conservative). Our results suggest that, when deriving RBSL using a specific tool, it is a prerequisite to technically review the analysis methods for cross-media transfer rates as well as to understand how the assessment tool derives the default values for exposure factors.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.241-246
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• 2017

The comparative results of corrosion testing in humid tropical atmosphere in rural and coastal areas for hot dipped zinc coatings are presented below. The test was conducted in outdoor conditions over a period of five years. The mass loss and other performance characteristics of two types of zinc coatings were evaluated, analysed and discussed in relation to the climatic and environmental parameters. The corrosion rates of the coatings exposed to coastal conditions were about three times higher than the corrosion rates appreciated in rural conditions. The data demonstrates that the corrosion process obeys an equation of the form $M=At^n$, where M is the loss of metal and t is the time of exposure. A and n are constants which values depend on the environmental characteristics and the physicochemical behavior of the corrosion products respectively. Corrosion is strongly influenced by atmospheric time of wetness (TOW) and airborne salinity. The nature and composition of corrosion products are also considered. Simonkolleite, a major crystalline phase, was found in the zinc corrosion products exposed to coastal conditions, while zinc hydroxide and zinc hydrosulfate are easily found in rural settings.