The corrosion performance of steel and reinforced concrete in a tropical humid climate. A review

A systematic study of atmospheric corrosion behavior of steel and reinforced concrete was carried out in a tropical, humid, marine-coastal and rural-urban test sites, located in the Gulf of Mexico, and the Peninsula of Yucatan, in Southeastern Mexico. The temperature and relative humidity complex, time of wetness, principal contaminants (SO2 and air-borne salinity) and pluvial precipitation are related to the steel corrosion mechanism and the formation of corrosion products. Regression analysis kinetics equations are presented. An electronic sensor was developed for monitoring the temperature and time of wetness of metal surface and the performance of concrete exposed in the tropical environment. The corrosivity of the marine-coastal and rural-urban atmospheres is classified according to ISO 9223-92. The atmospheric parameters and chloride deposition rate correlate well with the corrosion potential and current, time of curing, water/cement ratio and chloride content close to the bar of concrete specimens, exposed to the marine atmosphere and an accelerated environment in a salt spray chamber. The corrosion products formed on steel are iron oxyhydroxides (alpha, gamma and beta) and oxides, namely goethite, lepidocrocite, akagenite, hematite, magnetite and maghemite. It is observed a change in the alpha/gamma ratio during the corrosion process. The corrosion kinetics of the steel bars in reinforced concrete, exposed in the field and in accelerated tests, are modeled by a bilogarithmic equation: log (i(corr)) = a + b log (t).