Preparation and study of morphology of mesoporous anodic films grown on tin foil

Mesoporous anodic layers were obtained on high-purity tin foils in electrolyte of two types: 0.3 M oxalic acid and 1 M NaOH in various anodizing modes. It was demonstrated that in both cases at low voltages below 4 V barrier films form. In acidic electrolyte the formation of tin (II) oxalate was observed whereas in basic electrolytes SnO₂·nH₂O seems to be formed. At intermediate voltage values from 4 to 8 V mesoporous films may be obtained with average size of pores of 20-40 nm, mesopores are rather uniformly distributed along the surface. It was found that in contrast to alumina anode films no linear dependency between pore diameter and voltage was observed at anodizing of tin foil. At voltages above 8 V and/or long-term anodization the film cracks and the film split to separate islands.