Mild steel corrosion behavior in a coastal megacity relevant to China Pakistan economic corridor

Abstract This 2-year study investigated mild steel corrosion in Karachi, Pakistan, comparing findings with other major coastal cities. Karachi plays a strategic role in China Pakistan economic corridor (CPEC) project. International Organization for Standardization and American Society for Testing and Materials standards were used to measure atmospheric corrosivity (C), corrosion rates, time of wetness, pollutants, and corrosion products along with analytical techniques. Corrosion rates classified three urban test sites as C3, three marine test sites as C5, and two urban and two industrial test sites as C4. The power-linear function was used to predict corrosion rates and corrosivity categories over 20 years. Long-term predictions showed medium C3 for urban and industrial sites and high C4 for marine sites. Mild steel might be the most effective material at marine test sites (average corrosion rates of 383–416 µm y −1 ). Different quantities/morphologies of lepidocrocite, goethite, and magnetite were commonly present, and akaganeite was occasionally detected.