Lithium-aluminium hydroxide hydrate thin layers on Al based substrates - new ecological process for corrosion resistance increase

Some preliminary experimental results on development of non-conventional, environmentally friendly procedures to form new corrosion protective thin films on Al, based on lithium-aluminium hydroxides known as hydrotalcite coatings, are presented. Chemical conversion films on pure Al and AU4G1 Al alloy have been formed involving LiNO3-KNO3-LiOH based solutions, with/without a second step involving Ce (III) and Mn (VII) compounds. SEM pictures revealed a uniform layer, formed by crystallites with 200-300nm walls length. Corrosion experiments showed their excellent performances, materialised in corrosion currents of 0.1-0.2 muA/cm(2) and at least 168 hours of salt mist exposure with no aspect modification.