Jingmao Zhao

The effects of some anions on metastable pitting of 316L stainless steel

Abstract The effects of PO 4 3− , CrO 4 2− , SO 4 2− and NO 3 − anions on metastable pitting of 316L stainless steel in NaCl solutions were investigated using potentiostatic and potentiodynamic polarization tests. The four anions all retard nucleation of metastable pitting. The inhibition effect decreases in the order: PO 4 3− >CrO 4 2− >SO 4 2− >NO 3 − . The propagation rates of metastable pits are also decreased by the anions tested. Both metastable pitting potential E m and stable pitting potential E p increase almost linearly with the increase of each anion concentration, and have very close increasing slopes.

EIS evolution of anodised aluminium by cerium salt sealing in NaCl solution with exposure time

Abstract The sealing of porous anodic oxide film on aluminium 2024 involving immersion of the anodised aluminium in an aerated solution containing cerium salt under the application of pulse power at room temperature has been proposed as an alternative to dichromate sealing method. The sealing process shows some advantages. The corrosion behaviours of the anodised aluminium unsealed or sealed by dichromate and cerium salt respectively were investigated at different exposure times up to 30 days in 1M NaCl solution by means of electrochemical impedance spectroscopy, and the damage functions were calculated in this work. The results show that the damage functions of anodised aluminium sealed with cerium salt are lower than those unsealed or sealed with potassium dichromate. Cerium salt sealing provides a better corrosion resistance of anodised aluminium in NaCl solution for long exposure time than dichromate sealing.

Electrochemical behaviors of anodic alumina sealed by Ce-Mo in NaCl solutions

Abstract The elimination of toxic materials in sealing methods for anodic films on 1070 aluminum alloy was studied. The new process uses chemical treatments in cerium solution and an electrochemical treatment in a molybdate solution. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) were used to study the influences of sealing methods on the corrosion behavior of anodic films in NaCl solutions. The results show that the Ce-Mo sealing makes the surface structure and morphology of anodic films uniform and compact. Ce and Mo produce a cooperative effect to improve the corrosion resistance of anodic films. Anodic films sealed by Ce-Mo provide high corrosion resistance both in acidic and basic solutions.