Role of climatic conditions on corrosion characteristics of structural steels

Corrosion behaviour of low alloy (LASS) and plain carbon (PCSS) structural steels exposed in different types of climatic conditions and nature of rust formed on their surfaces have been studied after 2 years of exposures. The test sites were chosen to represent four types of environments who strongly influence the corrosion of metals and alloys. They include (a) humid–saline, (b) humid–saline–urban (c) humid–industrial and (d) plain dry–urban environments. Mass loss, Raman spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopic studies have been performed to study the corrosion behaviour and characterise the nature of rusts formed on these steels. Mass loss measurement technique has been used to determine the loss of thickness of steels during their atmospheric and salt spray exposures. Results indicate that the corrosion rate of steels is strongly influenced by the climatic conditions prevailing at the exposure sites. The presence of SO2 and salinity in the environments change the structure and protective properties of rust formed on the steels’ surface. Electrochemical impedance and cyclic polarisation studies of the steels in simulated environments have been performed to understand the mechanism of corrosion in different climatic conditions.