ばら積石炭船倉内の腐食を模擬した希硫酸環境における造船用鋼の腐食および腐食疲労

概要

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An acid corrosive environment of a coal cargo hold was reproduced experimentally by using immersions of coal. Immersion tests, crack growth tests, and corrosion fatigue tests were performed under dilute sulfuric acids on a ship structural steel plate. A pH decreased with passage of time in an exudation solution from coal, and the end point was pH 2. 5. Corrosion rates were obtained in exudation solution and in dilute sulfuric acids of pH 4, pH 3 and pH 2. It could be confirmed that the corrosion rate in a dilute sulfuric acid could be substituted for that in the exudation solution from coal. The conditions of the fatigue crack initiation, ΔK_<CF>, were obtained from the observations of corrosion pits by a scanning electron microscope. The ΔK_<CF> was 3 . 60 and 5 . 39 Mpa・ml/2 in H_2SO_4 at pH 4 and at pH2, respectively. The crack growth rates estimated under corrosive dissolutions were 5.63 × 10^<-10> and 1.90 × 10^<-9> m/cycle for ΔK_<CF> in above environments. Concerning corrosion fatigue, S/ N curves, Seq/Nc curves on modified MIL HDBK 5 and ΔK/Nc curves were discussed in comparison with corrosion fatigue in seawater.
社団法人日本船舶海洋工学会の論文