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.
In the electrodeposition of copper, some sort of additives such as brighteners like Bis-(3-sulfopropyl)-disulfide (SPS) are added to the bath to produce a smooth surface. But the deposited copper using this type of bath shows the physical property changes while being kept at room temperature. In this research, an additive that can prevent property changes was searched for and the explanation of why the additive has that effect was investigated. Adding Sodium 2-mercapto-1H-benzoimidazole-5-sulfonate dihydrate (2M-5S) enabled the prevention of physical property changes while keeping the surface smooth. Since the correlation of grain size and tensile strength of the deposited copper using the 2M-5S added bath followed the Hall-Petch equation, the property was thought to be dominated by grain size, and the prevention of property changes was thought to be caused by the prevention of re-crystallization due to the pinning effect of the impurities in the copper. 2M-5S was conjectured to react with Diaryl-dimethyl-ammonium-chloride Polymer (DDAC) and adsorb to the cathode together, which was also conjectured to be a possible cause of the increase of impurities incorporated into the copper.