温水中におけるCu–Ni–P合金の耐食性

抄録

Phosphorus Deoxidized Copper(C1220) and High Strength Coppers (C1862 and C5010) are typical JIS_H3300 copper alloy materials, generally used in heat–transfer units such as evaporators, condensers and other applications. Furthermore, Cu–Ni–P alloy have been progressed as a brand–new High Strength Copper. Previous findings have shown that Cu–Ni–P alloy has not only higher tensile strength yet superior ductility than conventional High Strength Coppers but also resistance to the ant nest corrosion which causes fatal leakage on common copper tubing used in heat exchangers in a short time service. However, there have been few studies on anti–corrosion properties of Cu–Ni–P alloy tube in which hot water flows. In order to clarify the corrosion resistance of Cu–Ni–P alloy in hot water, electrochemical measurement by potentiostatic polarization test was performed using natural soft water at 60°C of which chemical composition is likely to cause moundless type pitting corrosion. Potentiostatic polarization test revealed that Cu–Ni–P alloy showed extremely low current density similar to that of C5010, whereas C1220 and C1862 exhibited consistently increasing values. Surface observation of specimens found that numerous pits formed on C1220 and C1862 while significantly fewer ones were found either on C5010 or Cu–Ni–P alloy. EDS analysis of the corrosion products around pits detected Si in all specimens. The results indicate that Cu–Ni–P alloy has excellent anti–corrosion properties similar to C5010 in hot water of which chemical composition is likely to cause moundless type pitting corrosion.