In-situ ellipsometric study of lead sulfate film electroformation on lead in a sulfuric acid solution

摘要

The process of lead sulfate film formation on a Pb electrode in 0.5 M H{sub}2SO{sub}4 has been investigated using the in-situ ellipsometric technique complemented with scanning electron microscopic imaging. The quality of a polished lead electrode surface was first evaluated by spectroscopic ellipsometric measurements. The results of the present work confirm that the passive film has a two-layer lead sulfate structure. The mechanism of growth of the inner layer is explained by nucleation and athree dimensional growth model. The inner layer appears to be porous and Pb{sub}2+ ions diffuse through this semi-impermeable barrier. As a consequence, an outer layer of larger crystals is observed on SEM micrographs.