Corrosion behavior of steel in different atmospheric conditions

Abstract

Corrosion of metals makes a large impact on the economy of a ountry. Therefore, it is important to take remedial actions to prevent structures, machinery and vehicles from corrosion. Among the various types of corrosion the corrosion that occurs in the atmosphere is known as atmospheric corrosion and it accounts for more failures than other types of corrosion. To take preventive actions against atmospheric corrosion of metals, it is essential to study the corrosivity of the atmosphere by analyzing factors that influence it. The corrosivity of the atmosphere mostly depends on several atmospheric variables, such as relative humidity, temperature, rainfall, chloride deposition rate, pollutant gases like nitrogen and sulfur oxides. In order to study the severity of the atmosphere which promotes the metal corrosion three types of commonly used structural materials mild steel, stainless steel 304 and 316 were exposed in two different atmospheric conditions. Two corrosion test panels were placed in two geographical locations and loss of weight due to corrosion was continuously measured in all three types of metals. The atmospheric variables in the two locations were also continuously recorded. Finally, these data were fitted with the power model in order to predict the rate of corrosion under particular atmospheric conditions. With the predicted corrosion rate under a particular atmospheric condition it is possible to take ecessary preventive measures during the design or in the service of metallic structures, machinery and vehicles etc. The broad aim of this research work is to collect adequate data to develop a corrosion model to redict the corrosion rate in any atmospheric environment in Sri Lanka using measured atmospheric variables and thereby establish a 'corrosion map 'for Sri Lanka.