Oil Sands Bitumen Effect on Corrosion

Abstract Corrosion susceptibility of commonly used oil sands slurry pipeline materials was evaluated with and without bitumen coating on their surface. Both linear polarization resistance (LPR) and rotating cylinder electrode (RCE) experimental techniques were used to estimate corrosion rate in a model brackish water. Five material coupons were used: two corrosion susceptible coupons, two coupons from stainless steel and one from chromium carbide overlay material. The chromium carbide overlay material was excluded from RCE experiments. Several dissolved oxygen concentrations (from 1 ppm to 9 ppm) were studied using LPR whereas RCE testing was conducted only at 5 ppm and a rotational speed of 2000 rpm. All these conditions were selected based on industrial scale experience at oil sands mine sites. In general, similar corrosion rates were observed between corrosion susceptible materials, while corrosion rate increased with increased dissolved oxygen concentration irrespective of whether the coupons surface was coated with bitumen or not. Shear force (wall shear stress or pressure drop) tends to enhance corrosion rates irrespective of a bitumen surface coating for corrosion susceptible materials. However, bitumen on the surface tends to reduce the corrosion rate significantly. Measurable corrosion rates were observed from chromium carbide overlay coupons at dissolved oxygen levels higher than 2.5 ppm. Not surprisingly, negligible corrosion was observed on stainless steel materials irrespective of coupon surface or flow condition.