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Comparative study on corrosion protection properties of electroless Ni‐P‐ZrO 2 and Ni‐P coatings on AZ91D magnesium alloy
Author(s) -
Song Y.W.,
Shan D.Y.,
Han E.H.
Publication year - 2007
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200604033
Subject(s) - materials science , corrosion , coating , magnesium alloy , metallurgy , alloy , magnesium , dielectric spectroscopy , composite number , electrochemistry , composite material , chemistry , electrode
Electroless Ni‐P‐ZrO 2 and Ni‐P coatings on AZ91D magnesium alloy were prepared, and their corrosion protection properties were compared in this paper. The potentiodynamic curves and electrochemical impedance spectroscopy (EIS) of the coated magnesium alloy in 3.5% NaCl solution showed that the corrosion performance of Ni‐P‐ZrO 2 composite coating was superior to that of Ni‐P coating. The same conclusion was obtained with salt spray and immersion tests. The corrosion morphologies of two kinds of coatings with various immersion time intervals in 3.5% NaCl solution indicated that most corrosion products concentrated on the nodules boundaries of Ni‐P coating and blocked corrosion pit was the main corrosion form. For the Ni‐P‐ZrO 2 coating, tortuous nodules boundaries were not the weak sites of the coating and corrosion initiated from the nickel phosphor alloy around the nanometer powders. Open corrosion pits occurred on the composite coating surface, and the coating was corroded gradually. Thus, the Ni‐P‐ZrO 2 coating exhibited better corrosion protection property to magnesium alloy substrate than Ni‐P coating.