The primary goal of the study was to establish corrosivity category in accordance with ISO 9223 norm of the two test stations located at National Institute of Oceanography (NIO) and Karachi Port Trust (KPT) along the east southern coastal route of China Pakistan Economic Corridor (CPEC) project in Pakistan. Electrogalvanized mild steel test coupons were exposed for a period of 12 months from May 2014 to May 2015. Results indicated that for both NIO and KPT test stations the corrosivity category in term of corrosion rate (C5+) was not in agreement with the corrosivity category (C5) established by using the pollution category and time of wetness. Corrosion kinetic parameters n and correlation coefficient (R2) obtained for NIO were 1.58 and 0.98 and for KPT 1.43 and 0.95 respectively. Scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDS) showed the presence of simonkolleite at NIO while zincite and hydrozincite at KPT. Fourier transform infrared (FTIR) spectroscopy showed that the typical corrosion products formed on both test stations were simonkolleite and hydrozincite. XRD showed the presence of zincite at both test stations and hydrozincite only at KPT.

Atmospheric corrosion near the coastal areas of Karachi is a subject of great interest where seasonal variation of north Arabian Sea, high onshore activities, high levels of atmospheric pollutants, high humidity, and low temperature range affects the service life of structural materials. Mild steel test coupons were exposed at the two atmospheric corrosion stations located in National Institute of Oceanography (NIO) and Karachi Port Trust (KPT) along the coastal line of Karachi, Pakistan for a period of 12 months. During the exposure period, the sulfur dioxide and chloride levels, corrosion rates and kinetics parameters were determined. The corrosion rates are high on both sites, but the corrosivity found in NIO is higher (C5) than in KPT (C4). Scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDS), Fourier transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) were used to characterize the corrosion products. Lepidocrocite is the main compound in NIO corrosion products, while in KPT are goethite and magnetite. The composition and morphology of corrosion products help to explain the difference in the corrosivity of both sites.

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This study aims to examine atmospheric corrosivity, corrodants, and corrosion products of southeastern coastal area of China–Pakistan Economic Corridor as per ISO protocols 9223 and 9225, and ASTM standards G1, G50, G140‐02, D4458‐94, and D2010. Test sites are located at National Institute of Oceanography (NIO) and Karachi Port Trust (KPT) at the banks of the Arabian Sea. Electrogalvanized mild steel test coupons were exposed, and levels of corrodants (sulfur dioxide, chloride, and time of wetness) were measured for a period of 24 months, from May 2014 to May 2016. Corrosivity category C5+ is established in terms of the corrosion rate for both NIO and KPT test stations, which does not coincide with the corrosivity category C5 ascertained by employing environmental characteristics and atmospheric corrodants. Corrosion kinetic parameter “n” and correlation coefficient (R2) are 0.71 and 0.97 for NIO and 0.96 and 0.97 for KPT, respectively. Scanning electron microscopy/energy‐dispersive spectroscopy, Fourier‐transform infrared spectroscopy, and X‐ray diffraction spectroscopy have corroborated the presence of simonkolleite and hydrozincite, zinc oxide, zinc hydroxychloride, and zinc in corrosion products at both test sites.

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