Study On The Abnormality Of Steels Corrosion At Tropic Seashore Atmosphere

The corrosion problem spreads all over the each realm of national economy developments, a flood of components, facilities & establishments invalidation because of corrosion bring about enormous economy loss for the nation. Atmospheric corrosion of metals is the most widespread and serious among all of corrosion. The 50% economy loss resulting in various corrosion is accounted for invited metals atmospheric corrosion. Therefore, the metal corrosion in the atmospheric environment is studied, and its corrosion regulation and characteristics in the different environment are understood. It has very important theory meaning and extensive application value for reasonable choice of materials and homologous protection measures, control of corrosion rate in the atmosphere, extension of the service life of the equipments and material, reduction of economy loss resulting from corrosion, and so on.Carbon steel and low alloy steel is the most common use metal materials for every kind of components, equipment and engineering facilities. The long-term atmosphere corrosion regulation in demostic typical region environment satisfies the dynamics equation D = A·t~n (D — corrosion depth, μm; t— exposures time, year, A— constant, equal to corrosion depth of the first year and has something to do with environment and materials; n token the development trend of corrosion depth, changing extremely with the steels and the environment, but generally less than 1). It indicates that the corrosion rate of carbon steel and low alloy steel gradually decreases with the horary extension and tends in steady but not rising in the majority the region of our country. But the value of A is smaller in the tropical ocean atmospheric environment. The value of n is larger than 1( such as in Wanning and Qionghai), sometimes reaching 1.97, which predicates the corrosion products are non-protective in these regions. The corrosion rate has the rising trend continuously, that is so-called" abnormality" phenomenon.The author adopts that the steels of Q235 and Cor-TenA were exposed at Wanning site located in Hainan province of China. Samples were tested with different orientation, surface state, time, periods and distance to the sea. The corrosion products were analyzed with SEM and X-ray diffraction. The similar experiment in the seaside of Qingdao has been done that is contrast with Wanning. Temperature, humidity and concentration of Cl~- in test district were continuously examined, analyzed and researched.