| Corrosion Resistance Enhancement of Micro-Arc
Oxidation Ceramic Layer by Mg-Al-Co Layered Double
Hydroxide Coating |
Zhi Hu Wang,a Ju Mei Zhang,b Yan Li,a Li Jing Baia and Guo Jun Zhanga,*
Pages : 59-66
DOI : 10.1080/0371750X.2019.1708800 |
| Abstract |
| To improve the corrosion resistance of the ceramic layer prepared by micro-arc
oxidation (MAO) on magnesium alloy, a hydrophobic Mg-Al-Co layered double
hydroxide (LDH) coating was fabricated on MAO coated AZ31 magnesium (Mg) alloy
by using a simple in-situ growth method. The results showed that the LDH film covered
the MAO coating tightly, and it sealed the micro-pores and cracks in the MAO
coating successfully. As a result, the LDH film increased the water contact angle of
MAO coating from 10.35º to ~137.21º, and the hydrophobic LDH/MAO composite
coating increased the Ecorr of MAO coating from –1.47 to –1.39 V/SCE and decreased
the Icorr by about two orders of magnitude. The electrochemical impedance
spectroscopy results showed that the LDH/MAO composite coating achieved the
largest dimension of capacitive loop and the highest impedance at low frequency
compared to MAO coated and uncoated AZ31 Mg alloy. Therefore, the LDH/MAO
composite coating could provide long-term protection for Mg substrate from
corrosive environment due to its hydrophobic function, ion-exchange ability and
barrier effect. This work has significant meaning to the applications of Mg alloys.
[Keywords: Magnesium alloy, MAO ceramic layer, Layered double hydroxide,
Corrosion resistance] |
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