Efeito do tratamento térmico thermex via laminação a quente na resistência à corrosão do vergalhão CA-50

Abstract

The use of rebar as structural reinforcement of reinforced concrete shows the relevance of these materials in a large number of industrial sectors, particularly in construction and infrastructure. In this context, the rolling manufacturing allows obtaining a material with lower cost and good quality, according to the required specifications, remarkably when performing, in hot rolling, the Thermex heat treatment step, in which the improvement of the mechanical properties is obtained as a result of the microstructural transformations that occurred. These transformations also influence the corrosion resistance of the material, as the microstructural variations acquired by the heat treatment parameters can present different performances in terms of corrosion. In this work, the CA-50 rebar made of 1025 carbon steel was evaluated with regard to corrosion resistance, whose interest was in the effect of Thermex on this property. Electrochemical analyzes such as Open Circuit Potential, Linear Polarization Curves and Electrochemical Impedance Spectroscopy were carried out, and with the solutions of 250, 500 and 1000 ppm NaCl, helped to define the main corrosion parameters. In addition, Vickers Microhardness measurements indirectly verified the microstructural transformations that occurred during the treatment. The microstructural characterization by Scanning Electron Microscopy, in its turn, in addition to identifying the phases formed after the treatment, also characterized the morphology after the corrosion tests, revealing the presence of generalized and localized corrosion. The techniques used in the routes with and without Thermex allowed to highlight how the microstructure formed along the Thermex influences the differences obtained in the characterizations, impacting the rebar corrosion resistance.