Corrosion Resistance Of Ni-Base Alloy028in High Chlordion Environment

The effects of temperature、CO2partial pressure and CT concentration on CO2corrosion behavior and film forming characteristics of nickel base alloy028were studied. The compositions and structures of the passive films formed on nickel base alloy028at high temperature and high CO2partial pressure environment were investigated by X-ray photoelectron spectroscopy(XPS).The anti-corrosion mechanism was given.The results showed that in CO2corrosion environment, with the temperature,CO2partial pressure and CT concentration increased, uniform corrosion rate of nickel base alloy028also increased.The XPS results indicate that the passive films formed on nickel base alloy028in environment with CO2partial pressure of1.6MPa and the exposure temperature of170℃had a double-layer structure, i.e.. The outer layer is hydroxide of Ni,Cr and Fe. The inner layer is the oxides of Ni,Cr and Fe.The results showed that with the temperature increased, corrosion current density increased, corrosion potential decreased, so corrosion rate declined; with the CO2partial pressure and temperature increased, corrosion rate increased,and it had the lowest rate, when CO2partial pressure was1.5MPa, temperature was130℃and ClT concentration was80g/L;As the Cl" concentration increased,corrosion potential decreased and corrosion current density increased, corrosion resistance weakenend;The EIS showed that with the temperature increased, the radius of frequency capacitance was large, the protection of passive film also enhanced, with the CO2partial pressure and temperature increased, the radius of frequency capacitance decreased, the protection of passive film also weakener, As the Cl" concentration increased, the radius of frequency capacitance decreased,the protection of passive films reduced; Mott-Schottky analyses displayed that with the temperature increased, the impurity density of nickel base alloy028decreased, with the CO2partial pressure and temperature increased, the gap increased in the passive film,so the impurity density increased;With the increase of CT concentration, corrosion resistance of nickel base alloy028reduced, the donor concentrations of and acceptor concentrations of materials have increased, the possibility of localized corrosion was larger in defect region.