Corrosion products on the brass surface were characterized by voltammetry with a high alkaline electrolyte solution （6 M KOH＋1 M LiOH）. In addition to copper oxides （Cu₂O and CuO）, zinc oxide （ZnO） was also confirmed on corroded brass surfaces. Depending on corrosion conditions, the amounts of the respective oxides formed on brass surfaces were varied. In the corrosion test in which brass is immersed in a NaCl solution （by assuming dezincification corrosion）, Cu₂O was selectively formed, and then grew significantly in NaCl solution at the concentration of 0.1％ or less. However, when the concentration exceeded 1％, the formation of ZnO was newly confirmed. It was suggested that the formation and growth behaviors of the oxides on brass should be affected by the diffusion rate of zinc dependent on the concentration of NaCl solution.

In the present study, possible effect of deposits on the corrosion of copper pipes in concentrated cooling water has been examined. It was considered that during the localized corrosion of copper pipes, the cathodic process took place on the intact sites of carbonaceous films, whereas the anodic process occurred on their defective sites. The deposits covering the defects of carbonaceous films significantly affected the corrosion of copper pipes. In particular, the presence of iron rust strongly enhanced the anodic reaction, resulting in severe corrosion. The enhanced anodic reaction was attributed to the suppressed formation of a protective oxide film most likely due to the lower pH of the areas located beneath the iron rust. It was suggested that the pretreatment to form a protective copper oxide film onto the copper pipe surface inhibited the corrosion process beneath the iron rust deposit.