Qualitative assessment of chloride and sulphate influence on soil corrosivity

Abstract

External corrosion is a corrosion phenomenon due to the environment or surrounding of the structure. This paper discusses on the influence of chloride and sulphate element on corrosion resistance of steel coupon buried underground. The coupons were placed underground at seven different locations of various soil compositions covering east-coast of Peninsular Malaysia. A total of 132 of steel coupons were installed in a 1.0m-hole and exposed to the subsoil environment for a period of 12-months whereby a periodic retrieval of the coupon were done for every 3-months so that the dynamic growth of metal loss can be measured continuously over time. Soil resistivity test were conducted on the selected sites to determine its corrosiveness level. Parameters such as sulphate and chloride content were measured to correlate with the actual metal loss of buried steel coupons. Site with the highest content of chloride and sulphate yields the most severe loss of metal volume. The findings show that chloride and sulphate contents are highly influential upon corrosion growth rate.