Atmospheric Corrosion Monitoring Sensor in Corrosion Rate Prediction of Carbon and Weathering Steels in Thailand

Galvanic type atmospheric corrosion monitoring (ACM) sensors can distinguish wet and dry conditions of a surface by reporting spiked charge when there is an electrolyte film on the sensor. In this study, Fe–Ag type ACM sensor was exposed to monitor time of wetness (TOWACM) on carbon steel and weathering steel coupons at seven test stations in Thailand. Climate parameters were monitored by weather stations. Chloride and sulfur dioxide deposition rates were obtained by dry gauze and lead dioxide cylinder methods, respectively. The objective was to investigate the effects of TOWACM, climate, and aerosols on corrosion rate in Thailand tropical climate under high temperature, high relative humidity, and frequent monsoon-induced rainfalls. Multivariable linear regression model applied on the first-year corrosion rate yielded predictive equations for (1) inland areas-as a function of temperature (T) and relative humidity (RH) and (2) coastal areas-as a function of rainfall (RF) with TOWACM or chloride (Cl−) deposition rate. The first corrosion map of Thailand was proposed based on the predictive equations for corrosion rates of carbon steel and weathering steel.