Evaluation of Corrosion Susceptibility of Conventional Dual-Phase Steels Used in the Automotive Industry
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JMEPEG https://doi.org/10.1007/s11665-020-05175-0
Evaluation of Corrosion Susceptibility of Conventional Dual-Phase Steels Used in the Automotive Industry R. Vences-Herna´ndez, F. Reyes-Caldero´n, Julio C. Villalobos, H.J. Vergara-Herna´ndez, and J.A. Salazar-Torres (Submitted December 13, 2019; in revised form August 22, 2020; Accepted September 27, 2020) Because of the high demand for dual-phase (DP) steels in the automotive and construction industry, the present investigation focused on evaluating the corrosion resistance of three different commercial DP steels through electrochemical corrosion tests in conventional media (0.5 M NaOH, 3.5 wt.% NaCl, and 0.5 M H2SO4 solution). The potentiodynamic polarization test allowed us to determine the corrosion rate and the degradation mechanism as a function of DP steel type, test media, the amount of martensite fraction, and microstructure of DP steels. DP-270 steel presented a higher corrosion resistance in NaCl and H2SO4 solutions compared with other DP steels. Moreover, DP-590 steel showed a higher corrosion resistance in NaOH solutions, while the DP-789 steel had the worst performance in NaOH and NaCl. Electrochemical impedance spectroscopy tests were performed to determine the charge-transfer resistance values from the Nyquist plots and review if DP steels followed the same tendency as the results that were obtained in the potentiodynamic polarization test, the mechanism of degradation was attributed to a charge-transfer. The microstructural characteristics of DP steels showed us that better corrosion resistance is related to a better distribution of the martensitic phase. Keywords
corrosion, dal-phase polarization curves, wear
steel,
potentiodynamic
1. Introduction Dual-phase (DP) steels have the right balance between tensile strength and stamping, which allows the production of thinner sheets, while reducing manufacturing costs. These attributes give DP steels the capability to absorb the energy generated during impact, making DP steels ideal for the automotive industry and increasing the units safety features (Ref 1). The advanced high-strength steel application guidelines V5 (Ref 2) and the work performed by Fonstein (Ref 3) showed that up to 40% of the total steel that is used in the automobile structure is DP steel. Years ago, the possibility of replacing conventional construction steels with DP steels was considered (Ref 4). The outstanding mechanical properties of DP steels made it a clear candidate to replace pearlitic steels in the construction industry because of its higher corrosion resistance (Ref 5). The DP steel characteristics mostly depend on its microstructure, which consists of a second martensitic phase and a ductile ferritic matrix. The volume fraction of the second martensitic phase increases according to the tensile strength of the steel (Ref 6, 7). The DP steels are either hot or cold-roll processed; these cold-rolled steels are suitable for the manuR. Vences-Herna´ndez, F. Reyes-Caldero´n, Julio C. Villalobos, H.J. Vergara-Herna´ndez, a
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