AMT/APS Multilayered Films as Adherence Promoters for Epoxy Coatings on Carbon Steel—Part I: Influence of Curing Conditions on Anticorrosive Properties of AMT/APS Films in Saline Medium

The first part of this work evaluates the influence of the cure conditions on the preparation of 3-aminopropyl trimethoxysilane (APS) and the corrosion inhibitor 5-amino-1,3,4-thiadiazole-2-thiol (AMT) multilayered films onto AISI 1020 carbon steel. The steel samples were pretreated in a 10 −2 mol L −1 AMT solution for 3 h, immersed twice in a 5% v/v APS solution, and heat-treated at different temperatures and curing times. Regardless of the curing conditions used, electrochemical impedance spectroscopy (EIS) in 0.5 mol L −1 NaCl showed that the inhibitor pretreatment favored the formation of a more protective film when compared to the alkaline-treated steel, covered or not by AMT or APS thin films. The AMT/APS multilayered film cured at 100 °C and 80 min exhibited the best improvement in the anticorrosive properties among all of the films studied in this work, which was confirmed by potentiodynamic polarization (PP) experiments performed in the same electrolyte. XPS analysis of the selected AMT/APS film system revealed the formation of a Fe-O-S-R chemical bond, confirming the interaction of the AMT inhibitor with the NaOH-treated steel surface. The present findings indicate that the APS-AMT interaction may have occurred from the N-S bond, identified in the N 1 s spectrum.