Characterization of rare-earth conversion films formed on the AZ31 magnesium alloy and its relation with corrosion protection

By M. F. Montemor, A. Simões, M. Carmezim. 2007

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Abstract Two pre-treatments were studied for AZ31 Mg alloy substrates, consisting of immersion in cerium nitrate and lanthanum nitrate solutions for various immersion times. The surface composition was investigated by X-ray photoelectron spectroscopy and Auger electron spectroscopy that revealed the presence of a surface film containing the rare-earth cation, with a composition which was time dependent in the case of the cerium pre-treatment. The corrosion behaviour of the pre-treated substrates in 0.005 M NaCl solutions was assessed by potentiodynamic polarization, open circuit potential monitoring and the scanning vibrating electrode technique (SVET). The electrochemical results show that the pre-treatments reduced the corrosion activity of the AZ31 Mg alloy substrates in the presence of chloride ions. The corrosion protection efficiency is dependent on the treatment time.

Subfields: Biomaterials, Materials Chemistry, Mechanics of Materials

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