Estudo de revestimentos anticorrosivos epóxi-fosfato de zinco com adição de argilas montmorilonitas: aplicação em usina termelétrica

Abstract

Atmospheric corrosion is the most frequent degradation process in metallic materials exposed to air and its pollutants, such as chloride, sulfate and particulates. Steel and its alloys are the most popular and important metallic structural materials in the world. However, the problem of atmospheric corrosion of these materials must be considered during their applications. Currently, among the existing anticorrosive protection means, the application of organic coatings is one of the most used in the protection of metallic structures in industry, especially in the electrical sector, such as thermoelectric plants, against atmospheric corrosion. Epoxy resin based coatings are one of the most widely used types of polymeric films to protect steel structures against corrosion. The literature reports that the addition of zinc phosphate (ZnP) and montmorillonite (MMTs) clays improve the barrier performance of these coatings against corrosion. In this context, the objective of this work was to evaluate the behavior of anticorrosive coatings based on epoxy resin with and without the addition of ZnP and MMTs clays, at different concentrations, applied to carbon steel panels, through accelerated corrosion tests and exposure in Atmospheric Corrosion Stations (ACS's) in the particular condition of the Pecém thermoelectric complex. Electrochemical Impedance Spectroscopy (EIS) analyzes and visual inspections of the painted panels were used to evaluate the degradation process in relation to the exposure period. The EIE results indicated superior performance of the coatings produced with lower concentration of MMTs clays incorporated in the epoxy matrix. The coating with only ZnP added to the epoxy matrix showed better barrier performance. In general, the increase in the MMT clay concentration resulted in the reduction of the barrier properties of the coatings. The increase in the concentration of MMTs clays from 2% to 4% by mass affected the curing process of the coatings, showing lower crosslinking density (higher PVC/CPVC), reducing the barrier properties of coatings with a higher concentration of MMT clay. The performance of coatings with lower concentration of MMT clay, particularly in the ECA's evaluated at the thermoelectric plant site, was satisfactory. These painting systems studied in this work can be technically viable alternatives for paint maintenance on its metallic structures, as long as they present good anticorrosive performance.