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Corrosion and corrosion fatigue performances of micro‐arc oxidation coating on AZ31B cast magnesium alloy
Author(s) -
Xue Yuna,
Pang Xin,
Jiang Bailing,
Jahed Hamid
Publication year - 2019
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.201810293
Subject(s) - materials science , coating , corrosion , metallurgy , micro arc oxidation , microstructure , corrosion fatigue , alloy , magnesium alloy , composite material , conversion coating
In this work, the corrosion performances of micro‐arc oxidation (MAO) coating on AZ31B cast alloy were examined. MAO coating synthesized at a low current density of 34 mA/cm 2 has a uniform and compact microstructure with very fine micro‐pores and few structural defects; thus, robust protection is provided for the AZ31B substrate in corrosive solutions. The long‐term corrosion and corrosion fatigue behaviors of the MAO coatings formed at the optimal current density for 5 and 10 min were characterized. The results show that the MAO coating formed for 10 min provides greater protection in a salt fog environment than the coating formed for 5 min does because it is thicker. The fatigue life and fracture analysis of bare, MAO‐coated and E‐paint MAO‐coated AZ31B indicate that the MAO coating reduces corrosion fatigue life by 55% due to the micro‐pores and micro‐cracks on its surface providing initiation sites under stress conditions and accelerating crack propagation. However, E‐paint MAO‐coated specimens show improved corrosion fatigue strength in 10 7 cycles at ∼60 and ∼50 MPa under the same conditions due to the sealing of the micro‐pores and micro‐cracks in the MAO coatings.