In situ growth of Mg-Al hydrotalcite conversion film on AZ31 magnesium alloy

In situ growth of Mg-Al hydrotalcite conversion film on AZ31 alloy has been developed by a two-step method. The characteristics of the films were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electronic microscope (SEM) observation, electrochemical and immersion tests. The film formation process was proposed based on the open circuit potential (OCP) measurements and surface analysis. A precursor film with network cracks is first formed and then this film is transformed into a compact and uniform hydrotalcite (Mg(6)Al(2)(OH)(16)CO(3)center dot 4H(2)O) film after the post treatment. This dense Mg-Al hydrotalcite film can provide effective protection to the AZ31 alloy. (C) 2011 Elsevier Ltd. All rights reserved.