Influência da adição de xilitol em água de poro de concreto contra corrosão do CA-50

Abstract

This work aims to investigate and analyze the efficiency of xylitol as a green inhibitor to prevent corrosion of CA-50 rebar, and may be an alternative to replace sodium nitrite (currently used), even though it is harmful to both the environment and to health. The xylitol has no harmful properties to the environment or humans, is easy to obtain and is obtained by means of biotechnological techniques of sugarcane bagasse. CA-50 steel (rebar) is widely used to reinforce the concrete structure by being enveloped by it. Even if the rebar is surrounded by concrete, and the concrete in contact with water releases a solution of pH≈13, corrosion occurs. To study the efficiency of xylitol, CA-50 steel was exposed to solutions that simulated the medium inside the concrete (pore water - AP) in the presence and absence of xylitol and sodium nitrite, with or without sodium chloride. The concentrations of xylitol were 0.5%, 2%, 5%, 10%, 15% and 20% (w / v) of sodium nitrite was 2% (w / v). and sodium chloride was 3.5% (w / v). The CA-50 steel was immersed in the solutions (described above) and monitored by weighing and photographs, every 3 or 4 days for 19 days. Also, electrochemical studies were carried out, which consisted of measurements of open circuit potential, electrochemical impedance spectroscopy (EIS) and polarization curves. The monitoring results showed that all rebar immersed in solutions containing AP and sodium chloride presented oxidation and mass variation, including rebar immersed in solutions containing xylitol or sodium nitrite. The bias curves showed that the CA-50 steel immersed in the solutions of AP, AP with sodium chloride and AP with sodium chloride and sodium nitrite formed a passive layer, which contributes to the protection of CA-50 steel. In all the polarization curves obtained in solution containing xylitol, they showed an active behavior, indicating that xylitol does not contribute to the protection of CA-50 steel. In the Nyquist graph, the CA-50 steel immersed in the AP solution with sodium chloride and sodium nitrite, presented the highest capacitive arc when compared to the other samples, indicating that sodium nitrite is a better inhibitor when compared with xylitol. Concluding that xylitol does not present corrosion inhibitor behavior at the concentrations and conditions used.