PASSIVATION OF SUPERDUPLEX STAINLESS STEEL AFTER AN ACIDIZING TREATMENT

摘要

When acidization treatments are applied through stainless steel tubing, active corrosion can proceed very rapidly, the more so at elevated downhole temperatures. Although exposure to these aggressive environments is normally short and the formulations are normally inhibited, the steel should be capable of regaining passivity when production is resumed. A series of laboratory experiments was performed to simulate the effects of an hydrochloric acid treatment on super duplex steel with subsequent exposure to a sweet or mildly sour chloride brine at 150 deg C. From the results it became clear that re-passivation of the super duplex steel surface occurred, even without oxygen. Corrosion rates of the order of 0.1 mm/y were attained and may be expected to slowly decrease further upon prolonged exposure. It can be concluded that, in case of activation due to an acid treatment, re-passivation of super duplex stainless steel takes place for the investigated production conditions.