Deposits can play an important role in the corrosion rate and morphology of carbon steel in a production environment as well as affect the efficacy of an inhibitor. A test method has been developed to investigate the corrosion characteristics of carbon steel in a stratified flow regime where deposits of solids accumulate in the bottom of a pipeline. This test method is used to investigate the difference in under deposit corrosion of API X-65 carbon steel when the deposit consists of either sand or iron sulfide (FeS) with and without the presence of mill scale on the
steel. In the case of bare API X-65 carbon steel, the average corrosion rate of the coupons in the FeS deposit is significantly higher than those in the sand deposit, with metal thinning above the deposit and pitting at the solid / liquid interface. In the case of the carbon steel with mill scale, the average corrosion rate and the thickness loss of the coupons were relatively the same for the two deposits. Pitting occurred on the samples with mill scale in the sand deposit, though not in the FeS deposit.BR>
Keywords: under deposit corrosion, iron sulfide (FeS), sand, mill scale