Inhibition of 5083 aluminium alloy and galvanised steel by lanthanide salts

Lanthanide salts ale being considered its an environmentally friendly alternative to the classic systems based on chromates. The inhibitor behaviour of CeCl3 has been studied for both AA5083 alloy and galvanised steel in aerated NaCl solutions. For AA5083, cerium appears as dispersed islands whilst in the galvanised steel samples, it is stochastically dispersed onto the metallic surface, forming a film. These differences can be interpreted in terms of the distribution of cathodic areas for each material. In the case of AA5083, Al-6-(Mn,Fe,Cr) acts as permanent cathodic site whilst permanent cathodic sites do not exist in the galvanised steel. (C) 2000 Elsevier Science Ltd. All rights reserved.