Effects of Stannous Ion Concentration Flow Rate and Current Density on Tinplating by Phenolsulfonic Acid Bath.

We studied the effects of stannous ion concentration, flow rate, and current density on limiting current density, tinplate appearance, bright current-density-range, morphology, and orientation of deposited tin crystal, using a laboratory circulation cell and phenolsulfonic-acid-based baths.We found that (1) limiting current density increased and bright current-density-range broadened with increasing flow rate and stannous ion concentration, (2) the maximum bright current-density-range was near the limiting-current-density and increased with increasing flow rate and stannous ion concentration, (3) the minimum bright current-density-range increased slightly with increasing flow rate and stannous ion concentration, (4) fine tin crystals less than 1μm in diameter were closely deposited in the bright current-density-range, but coarse tin crystals of diameter more than 1μm were deposited below the range and many dendritic crystals were deposited above the range, (5) the iron exposure value (IEV) decreased with increasing current density, then increased, and over the current density of the lowest IEV at a low stannous ion concentration of 20g/L, the value increased greatly and increased slightly at a high stannous concentration of 50 or 80g/L, (6) the preferred orientation of tin deposited under the bright current-density-range was (100), but the (100) orientation decreased and (101) orientation increased with increasing the current density. In the bright current-density-range, the preferred orientation of deposited tin was (101).