Chromate and Chromate-Phosphate Conversion Coatings on Aluminium

摘要

Investigations of chromate and chromate-phosphate conversion coatings on aluminium using SIMS and AES techniques revealed that they are composed of hydrated chromium oxide/hydroxide and chromium phosphate respectively. These compositions are consistent with the electrochemical mechanism for conversion coating formation on aluminium. Enrichment of the outermost regions of the coatings with coating solution species suggests the gradual migration of these species under a concentration gradient towards the metal/coating interface where coating formation and growth consume such species.