INHIBITION OF STEEL CORROSIONIN 12 EDTA SOLUTION BY SIX N,S-COMPOUNDS

摘要

Carbon steel suffers severe corrosion during its immersion in the solution containing 12%rnammonium salts of ethylenediaminetetraacetic acid(EDTA) at elevated temperatures. SixrnN,S-compounds were selected as the inhibitor to investigate their inhibition efficiency in this corrosionrnsystem. Through coupon test and accelerated electrochemical study, highest efficient inhibitors werernchosen to formulate the alkaline pickling solution for the boiler used at elevated temperature.rnResulting from coupon test and electrochemical test, the six compounds reveal their inhibitionrnefficiency (%IE) decreasing in the order: 2-mercaptobenzothiazole (91%) >2-mercaptobenzimidazolern(84%) > benzotriazole (83%) > benzothiazole (81%) > indole (60%) > benzimidazole (59%).rn2-mercaptobenzothiazole (Mo) and 2-mercaptobenzimidazole (Mi) exhibiting the highest inhibitionrnefficiency among the compounds. The adsorption of both the inhibitor obeys the Langmuir adsorptionrnisotherm. XPS-analysis demonstrates that the highest efficiency of these two inhibitors is ascribed tornformation a strong Fe-S bond between the inhibitor and carbon steel. The density functional theoryrn(DFT) offers a rational illustration for the inhibition mechanism.