各種非シアン亜鉛メッキ浴の均一電着性

Abstract

Throwing power is one of the very important factors in zinc plating. It was determined in various plating baths such as high cyanide bath, low cyanide bath, zinc chloride bath, zincate bath, and pyrophosphate bath by means of Haring-Blum process, Watson process, and Bend cathode process.The results obtained were summarized as follows:1) Haring-Blum process was suitable for application in the baths for obtaining uniform plating in a wide range of current density. However, it was unsuitable in the baths likely to produce anodic passivity such as zincate and pyrophosphate baths.2) Watson process (Hull cell) was a very simple process in handling and of high utility. However, it was difficult to be applied in the baths for dendritic plating, because it gave burning in the part for measuring film thickness.3) Bend cathode process was suitable for application in the factory and was favorable for measuring film thickness on every face.4) Cyanide baths had considerably higher throwing power than the various non-cyanide baths. The decreasing order of throwing power of baths was arranged as follows: cyanide baths>zincate bath>pyrophosphate bath. The current efficiency in the above baths was promptly lowered with the increase in current density, and led to higher throwing power.5) Zinc sulfate bath had low throwing power.6) The throwing power of zinc chloride bath was higher with the decrease in Zn++ concentration and increase in NH4Cl concentration. It had higher throwing power than cyanide baths when ZnCl2 concentration was 30g/l or lower.