Pbフリー銅合金の耐食性  [in Japanese] Corrosion Resistance of Lead Free Copper Alloy  [in Japanese]

Pb has long been used as excellent anti-adhesion sliding material because of the soft metal, the ductility, the low shear, little-solubility and no compound formation in Fe. Pb-containing Cu-Sn alloy shows good sliding characteristics by forming the second phase of Pb in the alloy. However, the use of Pb is limited because it is harmful to the human body and the environment. Additionally, some kind of acid generated in the degraded oil corrodes Pb in Cu-Sn-Pb alloy, therefore the alloy decreases sliding characteristics. In this paper, we have studied Bi, soft material as well as Pb, as alternate material for Pb. To investigate corrosion resistance of these materials, we have conducted the electrochemical evaluation methods such as mixed-potential measurement method, anodic polarization method, and galvanic corrosion method on the basis of oil degradation test. As a result, we found that Bi has a better corrosion resistance than Pb, and Cu-Sn-Bi alloy has a better corrosion resistance than Cu-Sn-Pb alloy. In conclusion, we have developed Pb-free Cu-Sn-Bi alloy as alternate for Cu-Sn-Pb alloy.