Corrosion and tensile behavior of intercritically heat-treated and cathodically polarized prestressing steel wires

The effect of the intercritical heat treatments producing various martensite volume fractions on the corrosion and tensile behavior of the cathodically polarized prestressing steel wires has been investigated. Potentiodynamic polarization and constant extension rate technique (CERT) tests are conducted to clarify these effects and to determine the mode of failure of the prestressing steel wires since the presence of the martensite in the prestressing steel wire microstructure results in the failure and breakage during the corrosion and cold drawing. The electrochemical data measurements reveal that the intercritically heat-treated and cathodically polarized prestressing steel wires containing higher volume fractions of martensite exhibit the lowest corrosion potentials and current densities which indicate higher corrosion rates. A significant decrease in the tensile strength and ductility by the accelerated corrosion tests is observed in the intercritically heat-treated and cathodically polarized prestressing steel wire specimens containing higher martensite volume fractions. The fracture surfaces of the intercritically and cathodically prestressed steel wire specimens containing higher fractions of martensite of 68% exhibit a mixed mode of failure, i.e., quasi-cleavage and microvoid coalescence after potentiodynamic polarization. Moreover, the brittleness due to the residual stresses induced by the formation of martensite and the generation of the galvanic corrosion cell between the martensite and pearlite is noted to be increased with increasing the amount of martensite in the prestressed steel wire specimens.