Microstructure and Corrosion Behaviour of the Car Steels in Chloride Contained Environments

The DP980, DP590, and IF steels are used in the construction of car bodies due to their unique mechanical properties. In this paper, the corrosion behavior and microstructure of the DP980, DP590, and IF steels which are used in the automotive industry are investigated and evaluated. In order to evaluate the corrosion behavior of all three alloys, the electrochemical impedance spectroscopy and potentiodynamic polarization were evaluated in 0.1 M NaCl + 0.1 M H2SO4 and 0.1 M NaCl + 0.1 M NaOH environments. The corrosion evaluations of all three alloys show much better corrosion behavior in the alkaline environment than in the acidic environment due to the formation of the passive layer. While these alloys show much less corrosion resistance in the 0.1 M NaCl + 0.1 M H2SO4 environment, the uniform corrosion occurs while there is no evidence of the passive layer formation. The DP980 and DP590 dual-phase steels show lower corrosion resistance than the IF steel due to the presence of the ferrite and martensite phases and the possibility of galvanic cell formation at the interface between the two phases. The DP980 dual-phase steel has a better corrosion behavior than the DP590 due to the lower martensite content in both acidic and alkaline solutions, but the corrosion behavior of these two sheets of steel is very close to each other.