EIS Behavior of Experimental High-Strength Steel in Near-Neutral pH and Load Conditions

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2017-04, Vol.48 (4), p.1944-1958
• Main Authors: Barraza-Fierro, Jesus Israel, Serna-Barquera, Sergio Alonso, Campillo-Illanes, Bernardo Fabian, Castaneda, Homero
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion; Corrosion potential; Cracks; Electrochemical impedance spectroscopy; Ferritic stainless steels; High strength steel; High strength steels; Impedance; Low carbon steel; Materials Science; Metallic Materials; Microstructure; Nanotechnology; Steels; Stress corrosion cracking; Structural Materials; Surfaces and Interfaces; Thermal cycling; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-017-3973-5

Two thermomechanical heat treatments were applied to a high-strength low carbon steel with an experimental chemical composition, and as a result two different microstructures were obtained. Steel A had a ferritic microstructure, and steel B had a bainitic-martensitic one. The corrosion behavior was reviewed at long times in samples without load by means of Electrochemical Impedance Spectroscopy (EIS) in a near-neutral pH (NNpH) environment. The results showed that the quantity and adherence of corrosion products on the sample surface at long times are different. Hence, the impedance was higher for steel B. Slow strain rate testing (SSRT) was applied to tempered samples of the two steels at 473 K, 673 K, and 873 K (200 °C, 400 °C, and 600 °C), and the corrosion behavior was acquired using EIS at the same time as the SSRT in NNpH conditions. This is a novel result because the tension samples were not electrically isolated from the rest of the load frame. The impedance for the ferritic steel was higher than the bainitic–martensitic one, while it slightly decreased for both steel over time. Tempering improved the corrosion resistance for steel A, while it was not modified for steel B. The corrosion behavior could be associated with the susceptibility of these steels to stress corrosion cracking. A transmission line model was proposed to show qualitatively the corrosion behavior of a crack in the steel, if there is a potential profile inside the crack. A hypothetical potential profile was acquired as well as different impedance behaviors based on electrochemical variables.