Corrosion Behavior and Mechanical Property Degradation of Weathering Steel in Marine Atmosphere

This paper presents an experimental investigation into the corrosion behaviors and mechanical properties of weathering steel (WS) in a marine atmosphere. Two types of WS (Q420qNH and Q420qNHY) were tested, and carbon steel (Q420q) was chosen as contrast. First, as a simulated marine atmosphere environment, the neutral salt-spray accelerated corrosion test was conducted to study the corrosion mechanism of WS. Corrosion characteristics including corrosion evolution with time and surface morphologies of corroded specimens were obtained and compared among three types of steel. Then, tensile testing on corroded specimens was carried out to investigate the mechanical property degradation of WS. The digital image correlation (DIC) method was used to obtain the full-field strain of corroded specimens during the experiment. The effect of corrosion damage on the mechanical properties of the steels is discussed. Finally, the degradation mechanism of mechanical properties resulting from the local corrosion was determined by analyzing the surface strain of corroded specimens. Results show that Q420qNHY steel with much higher corrosion resistance was more applicable to the marine atmosphere because of the formation of a compact rust layer on the steel substrate surface. The corrosion morphology characteristics of three types of steel were different at the same corrosion time. Q420qNH and Q420qNHY steels presented a similar degradation degree of mechanical properties after corrosion, which was less than that of Q420q steel. However, according to the analysis on degradation of elongation, Q420qNH steel is not applicable to the marine atmosphere. The local corrosion accelerated the development of strain at the fracture section, which eventually resulted in the reduction of elongation with increasing corrosion degree. The different corrosion behaviors and mechanical properties of steels would significantly affect the service performance and life of bridges and should be considered during bridge design.