Characterization of atmospheric corrosion near the coastal areas of Arabian Sea

Abstract

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.

Atmospheric corrosion patterns of electrogalvanized mild steel at east southern coastal areas of CPEC

“…The present study showed that the value of n is higher than 0.5 for both test stations. This is indicating that the nature of corrosion product was non‐protective so mixed diffusion and charge transfer control happened …”

“…The concentration of chloride was moderate and falls in the S 2 category even though both test stations were marine. This may be due to the calm sea and vegetation along the shoreline which inhibits the air to carry the airborne salts from the sea . The concentration of sulfur dioxide was very high and fall in highest category P 3 which may be due to the emission activities of heavy cargoes and dumping of coal on the shore …”

“…Comparison of the results indicated that KPT test station was more aggressive for the electrogalvanized steel substrate as compared to NIO test station. This could be due to higher humidity and closeness to the sea …”

“…CPEC is the flagship of international project ‘One Belt One Road’ and anticipated as game changer in the region . Previously, the authors had explored the corrosivity data for some locations along Karachi coastal line using mild steel . However, no comprehensive atmospheric corrosion related study using galvanized steel has been executed in Karachi city so far.…”

Atmospheric corrosion kinetics and dynamics of electrogalvanized mild steel in southeastern coastal area of China–Pakistan Economic Corridor

“…[6,7] This study is in continuation of author's previously reported efforts to classify the corrosivity category of prevailing atmospheric conditions in Karachi, Pakistan. [6,8] The main purpose of this study was to classify the corrosivity category of the atmosphere of the two sites using ISO 9223 norm. The sites were located at National Institute of Oceanography (NIO) and Karachi Port Trust (KPT) along the southeastern coastal route of China-Pakistan Economic Corridor (CPEC) project in Karachi, Pakistan.…”