Evaluation of atmospheric exposure test on structural steel coated with different materials in the east of Thailand

The environment has a significant impact on the corrosion of steel. Corrosion is unavoidable; however, the rate of corrosion can be minimized by painting and galvanizing. The rate of corrosion depends on the coating and the environmental condition. The purpose of this research is to study and evaluate different types of structural steel coated with different materials in the East of Thailand. The atmospheric corrosion test is conducted for two types of steel, SS400 and SM490 with six different coating systems which are bare steel, hot-dip galvanized steel, hot-dip galvanized with painting (duplex system), common base practice paint steel, well base practice paint steel, and the premium base paint steel and the location of atmosphere corrosion test is conducted in three test site which is at Chachoengsao, Chonburi, and Rayong.Following the ASTM G50 standard, specimens are exposed to the real environment for three months, six months, and one year at the desired location. Weathering station at the test site collects and monitors environmental data such as temperature, rainfall, and relative humidity on a daily basis but the SO2 pollution, and airborne chlorides on a monthly basis. The weathering stations are present only at Station 13 Chachoengsao and Station 14, Chonburi. The sulfur dioxide was collected through a lead dioxide cylinder and the chloride was collected through the dry gauze method. The exposed steel specimen for bare steel and Hot dip galvanized are cleaned and the corrosion products are removed. After analyzing the thickness loss data of the specimens, we are able to predict the thickness loss of the specimens for bare steel and hot-dip galvanized steel and using the environmental parameters and the thickness loss data of one year we are able to predict first-year corrosion based on environmental parameters. The painted specimens are analyzed, and we can evaluate and compare different types of paint-coated specimens using the data. The results would indicate how the environmental parameters affect corrosion rate and able us to compare structural steel with various coatings. The results can be used to choose a coating, predict the steel’s service life, and predict thickness loss.