加熱した錫めっき銅板および黄銅板における錫めっき層の状態分析

Voltammetric technique using an ammonia buffer solution（0.5 mol/dm3 NH4OH＋0.5 mol/dm3 NH4Cl）was applied to ascertain the corrosion products formed on tin plating on pure copper or brass and to clarify the products' formation processes. The main corrosion products formed on tin plating in air were found to be SnO and SnO2･nH2O. Results further showed that SnO was formed in air at 180 ℃, although SnO2･nH2O was formed at 80 ℃ with high relative humidity of 90%. Copper/tin alloy layers in tin plating on copper grew with increased heating time. Analytical results show that the SnO film thickness on tin plating was lower than that on tin sheets. Moreover, characteristic behavior was shown for tin plating on brass in which Zn diffused rapidly to the surface under high-humidity conditions. The diffused Zn was oxidized to ZnO. However, the SnO amounts on tin plating on brass were lower than on pure copper.