アルコール+酸溶液中における金属材料の腐食

摘要

The corrosion behaviors of carbon steel(SS400), stainless steel(SUS304), titanium(Ti) and zirconium(Zr) in alcohol-HCl-H_2O solutions were investigated by performing electrode impedance measurement, polarization curve and immersion corrosion test, and the following results were obtained.rnCorrosion rate in acidic alcohol solutions increases with decreasing chain length of the alcohol in the following order ; methanol>ethanol>n-butanol. This finding can be mainly explained by the increase of the dielectric constant as the physicochemical property . When HC1 and H_2O were both in alcohol solutions, the corrosion rate of various metallic materials increased with increasing HC1 content, but decreased with increasing H_2O content in order to form the protective passivation film. H_2O/H~+ mol ratio in alcohol solutions is a factor which is very important for the passivation reaction process of metals . Titanium and zirconium in particular are easily passivated under H_2O/H~+ >1.5 in methanol solutions and H_2O/H~+>0.4 in ethanol solutions and consequently their corrosion rates decreased remarkably.This finding can be used as a corrosion attack prevention method.rnFurthermore, the corrosion resistance measured by the electrode impedance correlated closely to the corrosion rate estimated from the immersion corrosion test of various metals . Therefore, it is found that electrode impedance measurement is expected to be widely used as a rapid corrosion rate measurement method not only in aqueous solution but also in anhydrous solution such as alcohol.%非水溶液中において金属材料が激しく腐食することはよく知られており、当社においても本環境における腐食は多く発生している。しかしながら、非水溶液環境における腐食機構に開する文献は極めて少ない。このため、腐食防食技術の深化を目的に、非水溶液中における一連の腐食の研究に着手した。最初に研究に用いた非水溶液（有機溶媒）は、誘電率が大きく、電気化学測定が比較的容易と想定されるアルコール（メタノール，エタノール，n-ブタノール）である。