材料期刊网

Spontaneous electrochemical noise(EN)can be a rich source of information concern-ing the processes simultaneously occurring at a corroding interface.Potential noise fluctuations during the free corrosion of pure aluminum in different concentration of neutral sodium chloride solution are investigated,and the breakdowm and restoration of passive metal's film are studied using potentiodynamic scanning(PDS)measure-ments and electrochemical impedance spectroscopy(EIS)technique.Two capacitance loops are observed in the Nyquist plots in two kinds of concentration,and the corro-sion process is under activation control at first,then become diffusion control within the oxide film and corrosion products of (Al(OH)p-mClm^-)accumulated on the surface of the corroding electrode.It is suggested that the pitting corrosion is much easier to occur for pure aluminum in 7.0wtthan in 2.0wtaCl solution,and the high concentration of chloride ion in solution inhibits the repassivation of a metastable pit.The corrosion rate deterministic step does not involve Cl^-.