Influence of electric current characteristics of the formation process on the properties of PEO-coatings, obtained on MA8 magnesium alloy in potentiodynamic mode
It is established that in the potentiodynamic coating-formation mode by plasma electrolytic oxidation (PEO), the electrochemical and morphological properties of the resulting surfaces can be adjusted using the maximum current density. In this paper, the dependences of this value on such parameters as the maximum value and the rate of voltage change, as well as on the size of the oxidized product are obtained. The dependence of the protective properties of PEO-coatings obtained on magnesium alloy MA8 on the maximum density of the formation current is studied. Morphological and electrochemical studies of the obtained heteroxide layers were performed in order to identify the correlation of the coating properties with the density of the formation current. The main protective properties of PEO-coatings have been studied using scanning electron microscopy and potentiodynamic polarization. The results obtained indicate an increase in the thickness and porosity of coatings with an increase in the values of density of the formation current. It is shown that during the transition from low (2 mA/mm2) to high (up to 12 mA/mm2) maximum values of the current density, the polarization resistance has a maximum in range of 4 mA/mm2, which indicates the optimal mode of formation of PEO coatings with high barrier properties.