Effect of Micro - Arc Oxidation and Sealing Treatment on the Corrosion Resistance of Cast Al - Cu - Mg - Ag Alloy

ZENG Di - ping, LIU Zhi - yi, WU Hai - jiang, GUO Wen - min, CHEN Dong - rui

doi:10.16577/j.issn.1001-1560.2022.0224

Materials Protection >

2022 , Vol. 55 >Issue 8: 117 - 124

DOI: https://doi.org/10.16577/j.issn.1001-1560.2022.0224

Effect of Micro - Arc Oxidation and Sealing Treatment on the Corrosion Resistance of Cast Al - Cu - Mg - Ag Alloy

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(1. School of Mechanical and Energy Engineering, Shaoyang University, Shaoyang 422000, China;2. School of Materials Science and Engineering, Central South University, Changsha 410083, China)

Received date: 2022-02-22

Revised date: 2022-03-31

Accepted date: 2022-04-26

Online published: 2023-12-17

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Abstract

In order to enhance the corrosion resistance of the cast Al - Cu - Mg - Ag alloy, a micro - arc oxidation (MAO) coating was prepared on the surface of the alloy and then sealed with silicone epoxy resin. The corrosion resistance of the Al - MAO coating system before and after sealing treatment was analyzed by electrochemical test, salt spray test and full immersion test. Results showed that after the corrosion test, the cast Al - Cu - Mg - Ag alloy corroded seriously, a large number of corrosion pits appeared along the grain boundary, and the tensile strength of alloy decreased by about 60 MPa; as for the Al - MAO coating system, the corrosion medium corroded the alloy substrate through the micro pores on the surface of the coating, a large number of white spot - like corrosion products appeared on the surface, and its tensile strength decreased by about 25 MPa. The effects of sealing treatment on the Al - MAO coating were as follows: the corrosion current density reduced from 2.62×10-8A/cm2 to 5.52×10-12A/cm2; the corrosion potential positively shifted from -589 mV to -342 mV; the low - frequency impedance increased from～105 Ω·cm2 to ～109 Ω·cm2; after the salt spray test and the full immersion test, no corrosion occurred; and the tensile strength basically remained the same. After the sealing treatment, the surface defects of the MAO coating were sealed, and a dense ceramic - organic composite coating formed on the alloy surface, which greatly reduced the corrosion rate and significantly improved the corrosion resistance of the alloy system.

Key words： micro - arc oxidation; sealing treatment; electrochemical test; tensile strength; corrosion resistance

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ZENG Di - ping, LIU Zhi - yi, WU Hai - jiang, GUO Wen - min, CHEN Dong - rui . Effect of Micro - Arc Oxidation and Sealing Treatment on the Corrosion Resistance of Cast Al - Cu - Mg - Ag Alloy[J]. Materials Protection, 2022 , 55(8) : 117 -124 . DOI: 10.16577/j.issn.1001-1560.2022.0224

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