Analysis of the structural integrity of (Si3N4 and Al2O3) individuals coatings and the [Si3N4 /Al2O3]n heterostructure exposed to corrosive environments

In order to study the corrosive wear presented in the (Si3N4 and Al2O3) individual layers and the [Si3N4/Al2O3]n heterostructure as a function of the bilayers number (n = 1, 10, 30 and 70), exposed to a highly aggressive environments. This research presents a exhaustive analysis of the structural, chemical and surface properties, which influenced the corrosion response of these coatings. The results showed that the heterostructure presented better properties than the individual coatings, and that when the bilayers number increased, these properties also increased. Thus, the [Si3N4/Al2O3] heterostructure formed by 70 bilayers, presented values of 4.1 nm, 161 nm and 1.79% approximately for roughness, grain size and porosity factor, respectively, which represents a decrease of 51%, 82% and 23% of these properties in comparison to the heterostructure formed by 1 bilayer. Finally, these structural and surface conditions resulted in a 90% increase in polarization resistance and a 95% decrease in corrosion rate when comparing the n = 70 bilayers heterostructure with the n = 1 bilayer. Concluding that the [Si3N4/Al2O3] heterostructure formed by 70 bilayers presented the best set of properties to be implemented in highly corrosive environments.