Characterization of hydrophobic coating developed by micro arc oxidation on AA2014 alloy

Abstract

The interest in aluminum alloys is on account of their attractive properties and high strength to weight ratio. In marine environments aluminum alloys especially AA2014, exhibit low corrosion resistance. Micro arc oxidation (MAO), a novel technique, has gained popularity for synthesizing ceramic coatings by electrochemical treatment using an aqueous electrolyte on aluminum, magnesium, titanium and their alloys and it can be a method of improving corrosion resistance of aluminum alloys. In this study, a stable film is produced on the substrate of AA2014 aluminum alloy by MAO in an aqueous electrolyte having chemically treated with myristic acid. Corrosion properties of these treated and untreated surfaces are evaluated in freshly prepared 3.5% NaCl solution by potentiodynamic polarization test. The electrochemical measurements showed that the MAO treatment significantly reduced the corrosion current densities (<em>I</em>_corr) and simultaneously enhanced the corrosion potential (<em>E</em>_corr) values indicating that the surface becomes nobler than the untreated one. The surface morphology of the coatings is characterized by scanning electron microscope (SEM). Hydrophobicity of these coatings is evaluated by means of contact angle measurement by goniometer. XRD test is also done on the sample to find out present elements on the coating. For one of the treated surfaces the static contact angle for water is measured to be approximately 129°. Thus the coatings are found to offer excellent corrosion resistance combined with hydrophobic property.