2023 Volume 79 Issue 25 Article ID: 23-25006
The purpose of this study is to focus on the pitting corrosion of the outer water pipe surface, which was obtained in the external corrosion survey conducted by the Tokyo Metropolitan Waterworks Bureau. The relationship between the material, buried environment and the deterioration of the water pipe was analyzed using the survival time analysis. Therefore, we tried a new analysis of water pipe deterioration using the Kaplan-Meier method and Cox regression analysis, which have been applied in the fields of medicine and pharmacy in recent years. Based on these survey data, since there are cases in which pitting corrosion has been confirmed even in pipes coated with polyethylene sleeves (PS), analyzing the effects of the presence or absence of PS coating on the survival curve. As a result of the analysis, in the case of non-PS, it was newly revealed that the survival rate started to decrease from 40 years after the pipe laying, and decreased to 0.7 in about 70 years. Furthermore, it was shown by Cox regression analysis showed that the variables of geological features and pipe’s material did not contribute to the life extension effect of pipe with PS.
