Experimental investigation on gas-liquid two-phase slug flow enhanced carbon dioxide corrosion in vertical upward pipeline

The carbon dioxide corrosion behavior of API N80 grade steel enhanced by gas-liquid two-phase vertical upward slug flow has been both mechanistically and experimentally investigated. It is found that the hydrodynamic characteristics of slug flow, such as the direction alternated wall shear stress, the fluctuation of wall normal stress, and the mass transfer near the wall, have significant effects on the carbon dioxide corrosion process. It is difficult to form dense, compact, and protective corrosion product film in the corrosion process, which is dominated by general corrosion, and can develop into pitting and mesa attack due to localized corrosion. An empirical correlation is suggested to predict slug flow enhanced carbon dioxide corrosion. It is found that the mass transfer in corrosion product film can be neglected and the slug flow enhanced carbon dioxide corrosion is dominantly controlled by mass transfer or by both of mass transfer and electrochemical corrosion reaction.