Development of Al/Al2O3 at di̇fferent concentrati̇on and potanti̇al i̇n sulfuri̇c aci̇d (H2SO4) + sodi̇um molybdate (Na2MoO4)

In this study, The effect of different sodium molybdate (Na2MoO4) concentration (0.1-0.6 M) as additives, on anodizing process of 7075 aluminum alloy in sulfuric acid (0.4 M H2SO4) has been investigated. After the different potential (0.5-2 V) applied to the aluminum electrodes in sulfuric acid. AC impedance and current -potential curves were taken and optimal potential (2V) was determined. The most effective concentration was observed to be 0.5M at this determined potential. During anodizing process, different molybdenum oxides were formed by reduced at the cathode, depending on the concentrations of molybdate. For low molybdate concentrations, unstable molybdenum oxides with Mo between (Mo+4) and (Mo+5) are principally formed. For high concentrations, these unstable species are also produced but the stable molybdenum oxide with Mo close to (Mo+5) is principally formed. These different molybdenum oxides incorporate at the electrolyte/oxide interface. The corrosion behavior of the aluminum oxide formed on the surface (Al/Al2O3) has been evaluated with electrochemical impedance spectroscopy (EIS) and current -potential measurement in 3.5 % NaCl. This measurement has been supported with scanning electron microscope (SEM) images. According to results obtained, addictive has improved the quality (homogeneous, uniform and protective) of the surface oxide layer.