Pipeline steels in the presence of treated seawater used in the oil industry

The electrochemical noise technique was used to evaluate the corrosion behavior of the API X52 and API X65 pipeline steels in seawater treated with several chemical products in static conditions. This treated seawater is used in the secondary recovery system of the oil industry. The static conditions were selected to evaluate the corrosion behavior of the pipelines in a shutdown period where the seawater is stagnated inside the pipelines. The long-term current noise series in both pipeline steels show more perturbations in treated seawater compared to the API pipeline steels coupons exposed in the suction seawater used as control. The electrochemical noise patterns suggest a good correlation with the micrograph evidence founded in the corroded surfaces during the corrosion of API X52 and API X65 pipeline steels. The micrograph evidence suggests that at pitting index (PI, defined as the standard deviation of the electrochemical current noise divided by root mean square of the coupling current), mean value near 1. the localized corrosion was most severe. The presence of bacterial consortia influenced the trend of the PI values at the interval from 0.0.1 to 0.1, after 35 h.