Sn含有SUS 304系ステンレス鋼の硫酸水溶液中での腐食挙動
1988 年 37 巻 12 号 p. 732-739
詳細
1988 年 37 巻 12 号 p. 732-739
The effects of Sn content and simultaneous addition of selected alloying elements, such as Sn and Cu, each in slight amount, on the corrosion behavior of austenitic stainless steel of Type 304 have been investigated by using mainly electrochemical means in sulfuric acid solution. The main results obtained are summarized as follows: Sn exists in the matrix in solid solution, but is absent in nonmetallic inclusions. The corrosion rate in boiling 5wt% H2SO4 solution was remarkably reduced by addition of less than 0.5wt% Sn to the steel, and was further reduced by simultaneous addition of Sn and Cu. The reason why Sn improved the corrosion resistance of the steel was that the cathodic reaction and the anodic dissolution reaction in the active region were retarded by the presence of the surface film formed as a result of deposition of Sn in the form of oxides, SnO and/or SnO2. Therefore, until the film is formed on the steel surface, addition of Sn to the steel results in degraded corrosion resistance because of preferential dissolution of that element. Simultaneous addition of Sn and Cu makes the anodic reaction to retardation, and the resistance to dissolution in activated region to increase.
