Effects of atmospheric corrosion on fatigue properties of a medium carbon steel

The effects of atmospheric corrosion on fatigue properties were examined using a medium carbon steel, corroded in various atmospheres. Three different places, having various atmospheric conditions, were selected for the corrosion tests: (i) an industrial area, (ii) near the ocean, and (iii) beside a river in a hot spring region. A water and/or air electrochemical cell corroded the carbon steel to rust that had several forms, depending on the atmosphere. The form of the corrosion was distinguished visually and by spectroscopy. Strong oxidation occurred in all samples with the formation of rust. In addition, a more severe chemical reaction with chlorine was detected near the ocean although carbon was obtained in the industrial area. On the other hand, a high level of sulfur reacted with the sample near the river. Such chemical reactions gave rise to different corrosion mechanisms leading to different corrosion surfaces. A rough corrosion face with corrosion pits was obtained in two of the samples (industrial area and near the ocean), while a smooth surface was produced for the sample near the river. The change of the surface morphology clearly affected the fatigue strength, e.g., the rougher the sample surface, the lower the fatigue strength. On the basis of the corrosion system, details of the fracture and fatigue characteristics are discussed in the present work.