Corrosion behavior of API-5L-X42 petroleum/natural gas pipeline steel in South China Sea and Strait of Melaka seawaters

This work aims to investigate the corrosion effect of different seawaters surrounding Peninsular Malaysia on the carbon steel of the petroleum/natural gas pipeline. The Tafel extrapolation technique has been applied to evaluate the corrosion rate of the pipeline steel and different locations of natural seawaters have been used as the electrolyte solution. In this experiment, carbon steel pipeline, API-5L-X42 was utilized as the sample and the seawaters were taken from several locations in Peninsular Malaysia, specifically at the South China Sea (Terengganu, Kelantan, Pahang) and the Strait of Melaka (Melaka, Johor, Negeri Sembilan). The corrosion rate calculation and the type of corrosion attack also have been discussed on the basis of the mor-phology and the metal contents of the seawaters. It was found that the corrosion rate of the carbon steel is relatively higher in the Strait of Melaka seawaters than that of the South China Sea seawaters. The corrosion rate results varied from 0.01 to 0.024 mm/year. Immersion test were carried out to examine the corrosion product formed on the surface of the pipe and from the result, localized corrosion (pitting) and uniform corrosion occurred at the specimen's surface severely for both seawater electrolytes. In summary, South China Sea is more favorable en-vironment for the application of this type of pipeline steel compared to that of Strait of Melaka.