Comparative Evaluation of Induction Furnace Steel Rebars: Mechanical Properties, Microstructure, and High-Temperature Corrosion Behavior in Seawater

The present investigation provides a comparative quality evaluation of Grade-60 steel rebars produced by induction furnace (IF)-based industries. In addition to analyzing quality variations in different industrial processes, this study aims to evaluate their compliance with international standards such as ASTM A615/615M. Samples of rebars from six local producers were collected, and their chemical compositions, microstructural features, hardness profiles, and tensile properties, including yield and tensile strengths, were analyzed. A special focus was given to analyzing the case–core microstructure, the presence of martensite rings, and impurity density, which substantially affect strength and ductility. Additionally, the electrochemical investigation was conducted at different temperature ranges, from 50 °C to 100 °C. Potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) with open-circuit potential (OCP) was used to analyze the corrosion behavior of different samples in seawater. The finding suggests that the majority of rebars achieved the minimum requirements of ASTM 615 for Grade-60, except for some manufacturers, where minor deviation was noticed. However, significant variation in mechanical properties and chemical composition was observed among all six industries (A–F). Manufacturers are consistently exhibiting the highest mechanical properties, with a maximum yield strength of 580 MPa and tensile strength of 760 MPa (12 mm diameter sample). In contrast, various samples from E and F manufacturers recorded the lowest values, such as a minimum yield strength of 365 MPa (Industry F, 16 mm diameter) and a critically low elongation of 9.5% for sample E of 16 mm diameter. Microstructural analysis further confirmed the formation of martensite rim structures in samples of manufacturer A, evidencing the efficient thermomechanical treatment system installation in industries.