Consequences of Cold Drawing and Hot Rolling Processes on Microstructure, Microhardness and Electrochemical Corrosion of Structural Steels in 0.1 M Na2SO4, 0.1 M NaCl and Simulated Concrete Pore Solutions

In this work, the electrochemical corrosion of four structural steels, in the form of round bars coming from two thermo-mechanical treatments (cold drawing or hot rolling), was investigated separately in 0.1 M Na2SO4, 0.1 M NaCl, simulated concrete pore solution (SCPS) made of saturated 0.1 M Ca(OH)2, 0.1 M NaOH and 0.2 M KOH, and SCP solution with 0.1 M NaCl. Specimens were labeled as follows: TRA S235, LAM S275, LAM S355, and TRA S355, where TRA and LAM stand for cold-drawn and hot-rolled, respectively. An evaluation of the electrochemical corrosion properties was carried out through open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and anodic cyclic polarization (ACP) techniques. Furthermore, the surface or cross-section hardening and softening effects caused by cold drawing and hot rolling processes were monitored by Vicker's microhardness testing. Moreover, the structural and microstructural changes in steels due to thermo-mechanical treatments were characterized by means of XRD, OM and SEM-EDX analyses. Results obtained allowed to confirm the significant correlations between structural, microstructural, electrochemical, and microhardness changes with respect to the nature of the plastic deformation manufacturing process.