スケール分散剤・防錆剤共存下における銅管の孔食に及ぼすカーボン皮膜の影響

抄録

This study was performed to examine the suppression of pitting corrosion in copper tubes used for heat transfer in cooling water systems with absorption chillers. This corrosion was caused by the relation between the carbon film on the copper tube surface and the quality of the water flowing through the tubes. The water was treated with phosphonic acid and benzotriazole (BTA) to suppress pitting corrosion. Silicate and calcium ions effectively enhanced corrosion resistance of copper in the presence of phosphonic acid and BTA. We also studied the effects of chloride ions, which are known to have a corrosive effect, on copper pitting corrosion. We focused on the effects of carbon film on pitting corrosion of copper tubes in a system containing phosphonic acid, BTA, and silicate, calcium, and chloride ions. The potential was higher in copper tubes with higher residual carbon content. In the anode polarization curve measurements, current density was higher in copper tubes with lower residual carbon content. The potential range at constant current density was large for copper tubes with lower residual carbon content. These results suggested that copper tubes with low residual carbon content have excellent corrosion resistance.