Research on anti-corrosion property of rare earth inhibitor for X70 steel

Three kinds of rare earth nitrates were adopted to sodium molybdate to get three kinds of LnN-M compounded inhibitors （La（NO3）3＋Na2MoOa（LaN-M）, Ce（NO3）3＋Na2MoOn（CeN-M）, Pr（NO3）3＋Na2MoO4（PrN-M））. The combination of weight-loss method and the electrochemical test, was used to evaluate and analyze the corrosion inhibition efficiency of these LnN-M inhibitors to make the research on their corrosion inhibition performance, and the sequential order of their performance was found as follows： CeN-M〉 LaN-M〉PrN-M, among which, the inhibition efficiency of CeN-M for the X70 steel could reach 98.21%. The synergism parameters were calculated by weight-loss method, these computational data indicated that the synergistic effect between rare earth nitrates and sodium molybdate was obvious and significant. Surface morphology, chemical composition and phase components of the precipitation films were tested for discussing the mechanism of LnN-M inhibitors. The outer electronic configuration of the lanthanide was found to have an important influence on the inhibition efficiency. The CeN-M inhibitor was discovered to have the best inhibition effect with the amorphous cerium oxides. The results of this research revealed that the precipitation films formed on the surface of the steel samples had a crucial influence on the inhibition efficiencies after adding LnN-M inhibitors.