Author(s)

Takashi Iyasu¹, Motoki Kuratani², Itaru Ikeda³, Noriyuki Tanaka³, Yutaka Yamada², Osamu Sakurada²

¹Technical Support Department, Kurita Water Industries Ltd., Tochigi, Japan.
²Gifu University, Gifu, Japan.
³Technical Research Laboratory, DAI-DAN Co., Ltd., Saitama, Japan.

It is known that one of the causes of pitting corrosion of copper tubes is residual carbon on the inner surface. It was confirmed that type I” pitting corrosion of the copper tube is suppressed by keeping the residual carbon amount at 2 mg/m² or less, which is lower than that of the type I’ pitting corrosion, or by removing the fine particles that are the corrosion product of galvanized steel pipes. The developed water treatment chemical was evaluated using three types of copper tubes with residual carbon amounts of 0 mg/m², 0.5 mg/m², and 6.1 mg/m². The evaluation was conducted for three months in an open-circulation cooling water system and compared with the current water treatment chemical. Under the current water treatment chemical conditions, only the copper tube with a residual carbon amount of 6.1 mg/m² showed a significant increase in the natural corrosion potential after two weeks, and pitting corrosion occurred. No pitting corrosion and no increase in the natural corrosion potential were observed in any of the copper tubes that were treated with the developed water treatment chemical. In addition, the polarization curve was measured using the cooling water from this field test, and the anodic polarization of two cooling waters was compared. For copper tubes with a large amount of residual carbon, the current density near 0 mV vs. Ag/AgCl electrode (SSE) increased when the developed water treatment chemical was added.

Copper Tube, Pitting Corrosion, Residual Carbon, Cooling Water System, Water Treatment

Iyasu, T. , Kuratani, M. , Ikeda, I. , Tanaka, N. , Yamada, Y. and Sakurada, O. (2020) A Study of Water Treatment Chemical Effects on Type I” Pitting Corrosion of Copper Tubes. Materials Sciences and Applications, 11, 494-504. doi: 10.4236/msa.2020.117034.