極値統計的手法による鋼板および亜鉛系めつき鋼板の穴あき腐食現象の解析(自動車用鋼板)(<特集>表面処理)

概要

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The perforation corrosion of steel and galvanized steels due to the cyclic corrosion tests (CCT) has been analyzed by the extreme-value statistics. The plots of the maximum values of perforation corrosion depth and the cumulative probability gave straight lines and they were fitted to the Gumbel (Doubly exponential probability) distribution. The decrease of the slope of these lines with CCT time suggested that uniform corrosion occurred in an early stage of CCT but it changed to uneven corrosion with CCT time. The period of the uniform corrosion corresponds to the incubation time, t_i of perforation corrosion and t_i of the steel was extended proportionately with zinc coating weight. The perforation corrosion rate of Zn-Ni alloy electroplated steel after t_i was lower than those of other materials. This phenomenon seems to be attributable to formation of a protective corrosion product of ZnCl_2・4Zn(OH)_2 and a good adhesion of the product to the steel.
社団法人日本鉄鋼協会の論文
1986-06-01