Papers by Author: Jing Mao Zhao

Abstract: EIS is used in this paper to study the effects of anodic oxidation parameters on the film’s ability, and multi-layer equivalent circuits are proposed. The oxidation time has great effect on porous layer, the porous layer’s impedance increases as the anodic oxidation time prolong; anodic current density has effect on both barrier layer and porous layer, higher current density gets higher impedance values in both barrier layer and porous layer; anodic oxidation temperature has great effect on barrier layer, when the temperature decreases, the barrier layer’s impedance increases.

Abstract: Lithium ion was introduced into high purity aluminum (99.999%) by hydrotalcite precursor method, and Li/Al composite anodic film was obtained by anodizing. The methods of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the properties of the anodic film. The electrochemistry behaviors of composite anodic film were studied by means of potentiodynamic method and electrochemical impedance spectroscopy (EIS). The results showed that the composite anodic film was produced by hydrotalcite precursor method and which is amorphous to X-ray diffraction. The passivation current density of the anodic film in NaCl solution (1mol/L, pH=3, 7, 11) decreased obviously, while impedance value increased sharply. Corrosion resistance of the composite anodic film in NaCl solution was improved by the introduction of Li+ ion.

Abstract: The electrochemical behaviors of anodized and sealed aluminum alloys in NaCl solution were studied by potentiodynamic polarization, the open-circuit-potential and EIS. The results show that anodic oxidization of aluminum increases its corrosion resistance greatly. Different sealing methods have different influences on corrosion behavior of the anodized alloys in NaCl solution; corrosion resistance increases in the order: no sealing < water sealing < dichromate sealing < nickel fluoride sealing. The modulus of the porous film sealed by dichromate solution increases with the immersion time in NaCl solution, which is similar to the self-sealing effect of unsealed anodic films.

Abstract: With the certain deposition process, the conversion coatings by four different pretreatments on LF21 were studied. The morphology and the chemical composition of the conversion coatings were examined by scanning electron microscopy (SEM). The corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) and the salt spray test. The results showed that the different pretreatments had obvious effect on the cerium conversion coatings. For the certain deposition process, the optimal pretreatment process was identified.