Li-based conversion coatings on aluminium: An electrochemical study of coating formation and growth

The formation of inorganic conversions coatings on aluminium, without the aid of external polarisation have been studied involving lithium ions in the presence and absence of carbonate in alkaline solutions. Evidence of coating growth produced by open circuit measurements, cyclic voltammetry and electrochemical impedance spectroscopy points towards the formation of a lithium aluminate as pore filler in a matrix of previously produced aluminium hydroxide. Concentration of lithium and solution pH conditioned lithium availability for incorporation into the film. Coatings were found to be more stable in the absence of carbonate as suggested by the lower current densities displayed after lithium incorporation and associated overall higher resistance for the system.