石油タンク底板の腐食に対する環境因子の影響調査 石油タンク底板の防食技術の開発 第二報:-石油タンク底板の防食技術の開発 第二報-
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概要
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Considering corrosion problem on bottom plate of oil storage tanks, fundamental research especially on environmental effects to corrosion phenomena is carried out. From laboratory corrosion tests in sand, it is found that water content is the most important factor influencing localized corrosion, and, localized corrosion rate shows the maximum at 12wt% of water content. Lift of temperature and the chloride concentration also accelerate localized corrosion rate, but compared to water content, those effects are small. Statistical extreme value distributions of localized corrosion depth of SS400 steel and pure zinc show equal variation. By observations, localized corrosion occurs at metal surface where grain of sand adhered to, hence existence of oxygen concentration cell between inside of pit and surrounding airspace is estimated. From spray corrosion test, evolution of localized corrosion is also observed in spite of uniform wet surface condition. Chloride concentration is considered as acceleration factor of localized corrosion, but its effect is small at concentration less than 1000ppm. Statistical distribution of localized corrosion depth with SS400 steel and pure zinc also shows equal distribution according to double exponential distribution as same as corrosion tests in sand. From the the results described above on laboratory experiments and analysis, it is estimated that localized corrosion of bottom plate of oil storage tank takes place and develops by the formation of oxygen concentration cell. Based on the results considering field survey data, simulated corrosion test, which provides corrosion prediction of real tanks, came into view.
- 一般社団法人 日本高圧力技術協会の論文