Investigação da corrosão em revestimentos de óxidos anódicos depositados sobre ligas de alumínio por meio de tratamentos de plasma eletrolítico

Abstract

Plasma electrolytic oxidation (PEO) was employed to produce oxide coatings on a commercial aluminum alloy using electrolytes containing niobium (Nb), silicon (Si), and tungsten (W). Different anodizing times and initial electrolyte temperatures were evaluated to establish relationships between processing conditions, the morphological, chemical, and structural characteristics of the coatings, and their electrochemical behavior. Characterization was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and potentiodynamic linear polarization (PLP). SEM results revealed differences in layer thickness and morphology, including the formation of pores and microcracks, while EDS confirmed the presence of the incorporated elements. XRD analyses identified various alumina phases and phases associated with the incorporated elements, including WO3 in the tungsten-containing coatings. Polarization tests showed a significant reduction in corrosion current density compared to uncoated aluminum, particularly for the Nb-containing condition obtained at 15 °C for 3600 s. The results demonstrated that PEO coating performance stems from the interplay of composition, crystalline phases, thickness, morphology, and interface characteristics, with anodizing conditions playing a decisive role in achieving superior corrosion protection