Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016)
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM5
Anticorrosion yet Conductive Hf Coatings on AZ91D Magnesium Alloy by Magnetron Sputtering

Thursday, December 15, 2016, 9:20 am, Room Makai

Session: Advanced Protective Coatings/Stress Evolution, Nanostructure, and Physical Properties of Thin Films
Presenter: Zhoucheng Wang, Xiamen University, China
Authors: Z.C. Wang, Xiamen University, China
D.F. Zhang, Xiamen University, China
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Magnesium and its alloy are prone to corrosion due to the high electrochemical activity, although they are promising materials in electronics and aerospace industries . Surface coating technique has become an effective method to enhance the corrosion resistance of the Mg alloys. In addition to offering high corrosion resistance, the protective coatings should be conductive to avoid static buildup and maintain other advantageous properties when Mg alloy been used in the electronics and aerospace applications. In this study, anticorrosion yet conductive Hf coatings were fabricated on the AZ91D Mg alloys by magnetron sputtering with different bias voltages. The microstructure and corrosion behavior were investigated as a function of bias voltage range from 0 to -125 V. Both potentiodynamic polarization and neutral salt spray tests reveal that the Hf coating deposited at -100 V exhibits the best protective performance. It possesses the lowest corrosion current density of 1.032 mAc/m2 and the highest protection rate of 6, respectively. This perfect anticorrosion property is due to the dense structure and low porosity induced by applying the appropriate bias voltage. The chemical inert Hf oxide formed on the coating’s surface also contributes to improve the corrosion resistance. Various types of corrosion sites after corrosion tests are examined by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results indicate that the coating failure is determined by the synergy between the defects in coating and the random phase distribution in substrate.