Atmospheric Corrosion Behavior of Mild Steel with Different Cooling Modes After Austenitization

The present study investigates the atmospheric corrosion behavior of three different ferritic-pearlitic variants of mild steel, which were exposed to outdoor for 3 years. The corroded steel samples were retrieved at 1, 2, 3, 6, 18, 24, and 36 months of exposure, along with the weather report data (relative humidity, rainfall, and temperatures). After specified exposure, the corroded steel samples were retrieved for characterization (scanning electron microscope, Raman spectroscopy, and Fourier-transformed infrared spectroscopic techniques) and weight loss (mm/y) measurements. It has been observed that the corrosion rates of all steel samples are higher during the initial exposure and diminish with later exposure duration. This is attributed to the goethite (alpha-FeOOH) formation and its influence on the PAI (protective ability index) in the rust and compact rust layer with exposure. In addition, it has also been noticed that micro-galvanic attack within the pearlite colonies, as well as between pearlite and polygonal ferrite, are the main causes of corrosion during the initial stages. However, all the steel samples exhibited nearly the same corrosion rate after 3 years of exposure.