Effect of Citric Acid Passivation on the Marine Atmospheric Corrosion Resistance of L80 - 13Cr Stainless Steel

13Cr stainless steel is commonly used as the material of downhole tools in the field of offshore oil &gas exploitation,but it is prone to be corroded when stored in marine atmospheric environment.In order to improve the corrosion resistance of 13Cr stainless steel in marine atmosphere,the single citric acid passivation and citric acid-hydroxide composite passivation were selected to deal with the surface of L80-13Cr stainless steel,and their effects on the corrosion resistance of L80-13Cr stainless steel were investigated by polarization curve,FeCl3 pitting corrosion test,neutral salt spray test,outdoor exposure test in marine atmospheric environment and etc.Additionally,the reasons for the improvement of the corrosion resistance of L80-13Cr stainless steel resulting from citric acid passivation treatment were analyzed.Results showed that the two citric acid type passivation methods could significantly improve the marine atmospheric corrosion resistance of L80-13Cr steel and could ensure that the L80-13Cr steel presented no obvious corrosion in marine atmospheric environment for at least 3 months.This improvement was attributed to the fact that the citric acid passivation greatly increased the content of Cr-related compounds in the passive film of L80-13Cr steel,and thus improved the protectiveness of passive film.More importantly,the addition of hydroxide passivation treatment on the basis of citric acid passivation was helpful to improve the proportion of metal oxides in the passive film,thus further intensified the stability and corrosion resistance of passive film.Therefore,the comprehensive protection effect resulting from the citric acid-hydroxide composite passivation treatment on L80-13Cr steel was superior to that of single citric acid passivation treatment.