Determination of Chemical Species Dominating the Corrosivity of Japanese Tap Water by Multiple Regression Analysis: Fid-Bau Portal

Determination of Chemical Species Dominating the Corrosivity of Japanese Tap Water by Multiple Regression Analysis

Yuji Nakamura / Yasuki Matsukawa / Shinji Okazaki / Shukuji Asakura

Japanese tap water is Ca²⁺-poor and SiO₂-rich in comparison with that of other counties. Thus, there have been few studies on its corrosivity. We sampled tap waters at 70 different sites and in different seasons in Japan, subjected the samples to chemical analysis and measured localized corrosion depth and the total corrosion loss of carbon steel placed in these waters. The average corrosion rate v_avg and maximum localized corrosion rate v_max were calculated. The ratio of v_max to v_avg, which was defined as localized corrosion factor LCF (=v_max/v_avg), was also studied. The multiple regression method was applied to obtain the dependence of v_avg (objective variable) on concentrations of chemical species (explanatory variables). In the same manner, the relation of v_max and LCF to concentrations of chemical species was derived. As a result, we showed that SiO₂ and SO₄²⁻ mainly dominate the corrosivity of Japanese tap water. In particular, as SO₄²⁻ increased, v_avg became larger and v_max became smaller. Also, as SiO₂ increased, v_max became larger and v_avg became smaller. The behavior of LCF was similar to that of v_max. The findings of this study will be useful for estimating the corrosivity of tap waters that have low Ca²⁺ and high SiO₂ concentrations.