Protective Properties of Micro-arc Oxidation/Organic Composite Coatings on Surface of AZ91-Ti Composites

GU Yongrui; JIAO Jinchao; ZHANG Jin; LIAN Yong; ZHENG Kaihong

doi:10.16490/j.cnki.issn.1001-3660.2025.15.005

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Surface Technology ›› 2025, Vol. 54 ›› Issue (15) : 56-68. DOI: 10.16490/j.cnki.issn.1001-3660.2025.15.005

Technology and Application

Protective Properties of Micro-arc Oxidation/Organic Composite Coatings on Surface of AZ91-Ti Composites

GU Yongrui^{1, 2}, JIAO Jinchao^{1, 2}, ZHANG Jin^{1, 2, *}, LIAN Yong^{1, 2}, ZHENG Kaihong³

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Abstract

This study systematically investigates the long-term protective properties and under-film corrosion behavior of micro-arc oxidation (MAO)/organic composite coatings on AZ91-Ti magnesium matrix composites. Two coating systems are developed: a conventional epoxy-polyurethane (EP/PU) coating and an MAO/EP/PU composite coating. A MAO layer is fabricated under optimized electrochemical conditions, resulting in a uniform ceramic coating with a thickness of (20±3) μm. Both coatings are evaluated through a neutral salt spray test, electrochemical impedance spectroscopy (EIS), scratch test and so on to analyze their corrosion resistance and failure mechanisms. ||| The electrochemical test reveals that the MAO/EP/PU composite coating exhibits superior barrier properties, with an initial impedance value of 3.04×10¹¹ Ω·cm² compared with 1.78×10¹¹ Ω·cm² for the conventional EP/PU coating. After 960 hours of salt spray exposure, the MAO/EP/PU system maintains a significantly higher impedance value (7.81×10¹⁰ Ω·cm²), while the EP/PU coating shows severe degradation. Macroscopic observations confirm these results, with the EP/PU coating developing visible blistering after 720 hours, whereas the MAO/EP/PU coating remains intact throughout the test period. ||| The adhesion test demonstrates that the MAO interlayer improves the interfacial bonding strength, with initial adhesion values of 3.13 MPa for MAO/EP/PU compared with 3.01 MPa for EP/PU. The degradation in adhesion over time is attributed to structural changes in the organic coating and stress accumulation from under-film corrosion. The EP/PU coating exhibits localized and filiform corrosion propagation, while the MAO layer effectively suppresses the lateral spread of corrosive media, enhancing the composite coating's durability.||| The scratch test results further validate the superior protective capability of the MAO/EP/PU coating system. After 120 hours of salt spray exposure, the conventional EP/PU coating exhibits significant corrosion propagation with an affected area reaching 5.51 cm². In striking contrast, the MAO/EP/PU-coated AZ91-Ti demonstrates remarkable corrosion resistance, showing a limited corrosion extension area of approximately 3.00 cm² comparable to the property observed on coated AZ91 magnesium alloy under identical conditions. As the exposure time progresses, the EP/PU coating experiences complete failure, with the substrate surface entirely compromised by corrosion. For the MAO/EP/PU system, while maintaining overall protection, the AZ91-Ti composite begins exhibiting accelerated corrosion in later stages. This phenomenon is attributed to galvanic corrosion effects between the magnesium matrix and Ti particles, which becomes increasingly pronounced as the test duration extends. The final corrosion expansion area reaches 0.85 cm², which exceeds the 0.44 cm² of AZ91. |||In summary, the MAO interlayer significantly enhances the corrosion resistance of AZ91-Ti composites by improving interfacial bonding strength and blocking corrosive media penetration. The composite coating system enables AZ91-Ti to achieve protection levels equivalent to commercial AZ91 magnesium alloy, demonstrating its potential for practical applications in demanding environments. The findings provide valuable insights into the development of advanced protective coatings for magnesium matrix composites, particularly those containing Ti reinforcements. Future research should focus on optimizing coating processes to enhance bonding strength and evaluating long-term protective property under various environmental conditions.

Key words

Ti particle-reinforced magnesium matrix composites / micro-arc oxidation / air spraying / corrosion resistance / under-film corrosion

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GU Yongrui, JIAO Jinchao, ZHANG Jin, LIAN Yong, ZHENG Kaihong. Protective Properties of Micro-arc Oxidation/Organic Composite Coatings on Surface of AZ91-Ti Composites[J]. Surface Technology. 2025, 54(15): 56-68 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.15.005

References

[1] ESMAILY M, SVENSSON J E, FAJARDO S, et al.Fundamentals and Advances in Magnesium Alloy Corrosion[J]. Progress in Materials Science, 2017, 89: 92-193.
[2] SONG J F, SHE J, CHEN D L, et al.Latest Research Advances on Magnesium and Magnesium Alloys Worldwide[J]. Journal of Magnesium and Alloys, 2020, 8(1): 1-41.
[3] YANG H, CHEN X H, HUANG G S, et al.Microstructures and Mechanical Properties of Titanium- Reinforced Magnesium Matrix Composites: Review and Perspective[J]. Journal of Magnesium and Alloys, 2022, 10(9): 2311-2333.
[4] PU D M, WU S F, YANG H, et al.Effect of Ti Particles on Microstructure and Mechanical Properties of TiP/AZ91 Composites[J]. Journal of Materials Research and Technology, 2023, 22: 1362-1374.
[5] CUI J H, YANG H, ZHOU Y X, et al.Optimizing the Microstructures and Enhancing the Mechanical Properties of AZ81 Alloy by Adding TC4 Particles[J]. Materials Science and Engineering: A, 2023, 863: 144518.
[6] JIAO J C, ZHANG J, LIAN Y, et al.Influence of Micro/Nano-Ti Particles on the Corrosion Behavior of AZ31-Ti Composites[J]. Acta Metallurgica Sinica (English Letters), 2024, 37(3): 484-498.
[7] 冀盛亚, 常成, 常帅兵, 等. 医用镁合金微弧氧化/有机复合涂层的研究现状及演进方向[J]. 表面技术, 2023, 52(12): 315-334.
JI S Y, CHANG C, CHANG S B, et al.Research Status and Evolution Direction of Micro-Arc Oxidation/Organic Composite Coating on Medical Magnesium Alloy Surface[J]. Surface Technology, 2023, 52(12): 315-334.
[8] 曾娣平, 刘志义, 吴海江, 等. 微弧氧化及封孔处理对铸造Al-Cu-Mg-Ag合金耐腐蚀性能的影响[J]. 材料保护, 2022, 55(8): 117-124.
ZENG D P, LIU Z Y, WU H J, et al.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.
[9] GE Y F, JIANG B L, LIU M, et al.Preparation and Characterization of the Micro-Arc Oxidation Composite Coatings on Magnesium Alloys[J]. Journal of Magnesium and Alloys, 2014, 2(4): 309-316.
[10] 于阳. 电控箱体用镁合金复合涂层的设计及性能研究[D]. 西安: 西安工业大学, 2015: 20-28.
YU Y.Design and Performance Study of Magnesium Alloy Composite Coating for Electronic Control Box[D]. Xi'an: Xi'an Technological University, 2015: 20-28.
[11] YANG W, XU D P, WANG J L, et al.Microstructure and Corrosion Resistance of Micro Arc Oxidation Plus Electrostatic Powder Spraying Composite Coating on Magnesium Alloy[J]. Corrosion Science, 2018, 136: 174-179.
[12] CHENG S T, LIU Z, ZHU Z Y, et al.Effect of Micro-Arc Oxidation/Gravel Epoxy Composite Coating on Electrochemical Behavior and Wear Resistance of Rolled AZ31B[J]. Materials Today Communications, 2025, 42: 111260.
[13] 张秀萍, 穆耀钊, 李雷, 等. 镁合金表面有机防腐导电涂层的制备及性能研究[J]. 表面技术, 2019, 48(11): 341-346.
ZHANG X P, MU Y Z, LI L, et al.Preparation and Properties of Organic Anticorrosive Conductive Coating on Magnesium Alloy[J]. Surface Technology, 2019, 48(11): 341-346.
[14] DONG J Y, ZHONG J Q, HOU R X, et al.Polymer Bilayer-Micro Arc Oxidation Surface Coating on Pure Magnesium for Bone Implantation[J]. Journal of Orthopaedic Translation, 2023, 40: 27-36.
[15] JIAO J C, GU Y R, ZHANG J, et al.The Growth Behavior and Performance of Microarc Oxidation Coating on AZ91/Ti Composite: Influence of Ti-Reinforcement Phase and Electrolyte[J]. Journal of Magnesium and Alloys, 2025, 13(3): 1160-1175.
[16] ESFARJANI A, SHOKRIEH M M.Effects of TiO₂ Nanoparticles and Silane Coupling Agents on the Adhesion Strength and Weathering Properties of Silicone Rubber Coatings[J]. International Journal of Adhesion and Adhesives, 2024, 130: 103604.
[17] MAYER P, LUBECKI M, STOSIAK M, et al.Effects of Surface Preparation on the Adhesion of UV-Aged Polyurethane Coatings[J]. International Journal of Adhesion and Adhesives, 2022, 117: 103183.
[18] LJ S Ž, JEGDIĆ B V, POPIĆ J P, et al.The Influence of Ce-Based Coatings as Pretreatments on Corrosion Stability of Top Powder Polyester Coating on AA6060[J]. Progress in Organic Coatings, 2013, 76(10): 1387-1395.
[19] BAJAT J B, DEDIĆ O.Adhesion and Corrosion Resistance of Epoxy Primers Used in the Automotive Industry[J]. Journal of Adhesion Science and Technology, 2007, 21(9): 819-831.
[20] VERMA G.Weathering, Salt Spray Corrosion and Mar Resistance Mechanism of Clay (Nano-Platelet) Reinforced Polyurethane Nanocomposite Coatings[J]. Progress in Organic Coatings, 2019, 129: 260-270.
[21] CAI G Y, WANG H W, JIANG D, et al.Degradation of Fluorinated Polyurethane Coating under UVA and Salt Spray. Part I: Corrosion Resistance and Morphology[J]. Progress in Organic Coatings, 2018, 123: 337-349.
[22] HUANG Y W, SUN X L, SONG J L, et al.Study on Corrosion Protection Behavior of Magnesium Alloy/ Micro-Arc Oxidation Coating in Neutral Salt Spray Environment[J]. International Journal of Electrochemical Science, 2023, 18(7): 100179.
[23] ZHANG J, ZHENG Y Y.Constructing Multi-Protective Functional Polyurethane Composite Coating via Internal- External Dual Modification: Achieving Superhydrophobicity, Enhanced Barrier, Corrosion Inhibition, and UV Aging Resistance Properties[J]. Progress in Organic Coatings, 2024, 194: 108540.
[24] 李迎超, 高瑾, 李晓刚, 等. 扫描Kelvin探针研究缺陷涂层的膜下腐蚀电化学行为[J]. 北京科技大学学报, 2010, 32(9): 1169-1174.
LI Y C, GAO J, LI X G, et al.Research of Electrochemical Corrosion Behavior under Coatings with Defects by Scanning Kelvin Probe[J]. Journal of University of Science and Technology Beijing, 2010, 32(9): 1169-1174.
[25] CRISTOFORETTI A, ROSSI S, DEFLORIAN F, et al.Recent Progress in Understanding Filiform Corrosion on Organic Coated Steel: A Comprehensive Review[J]. Progress in Organic Coatings, 2024, 192: 108469.
[26] ZHOU L, LU H L, ZHENG X H, et al.Preparation of Superhydrophobic Coatings on 6061 Aluminum Surfaces by MAO and Self-Assembly of PFDTES and Study of Their Property[J]. Progress in Organic Coatings, 2025, 200: 109022.
[27] 王东, 刘金玉, 孙世博, 等. 镁合金表面微弧氧化/自组装/镍复合涂层的腐蚀过程和机理[J]. 中国表面工程, 2024, 37(1): 100-109.
WANG D, LIU J Y, SUN S B, et al.Corrosion Process and Mechanism of Micro-Arc Oxidation/Self-Assembly/ Nickel Composite Coating on Magnesium Alloy[J]. China Surface Engineering, 2024, 37(1): 100-109.
[28] 张杨广, 陈跃良, 卞贵学, 等. 铝合金丝状腐蚀研究综述[J]. 表面技术, 2020, 49(12): 116-126.
ZHANG Y G, CHEN Y L, BIAN G X, et al.A Review of Research on Filiform Corrosion of Aluminum Alloy[J]. Surface Technology, 2020, 49(12): 116-126.
[29] 满成, 国景一, 孙议祥, 等. 典型防护涂层体系在南极大气环境中的失效行为研究[J]. 表面技术, 2022, 51(6): 27-35.
MAN C, GUO J Y, SUN Y X, et al.Failure Behaviour of Some Classical Protective Coatings in Antarctic Environments[J]. Surface Technology, 2022, 51(6): 27-35.
[30] 王贵容, 郑宏鹏, 蔡华洋, 等. 环氧防腐涂料在模拟海水干湿交替条件下的失效过程[J]. 中国腐蚀与防护学报, 2019, 39(6): 571-580.
WANG G R, ZHENG H P, CAI H Y, et al.Failure Process of Epoxy Coating Subjected Test of Alternating Immersion in Artificial Seawater and Dry in Air[J]. Journal of Chinese Society for Corrosion and Protection, 2019, 39(6): 571-580.
[31] 胡巍. 紫外/盐雾耦合环境下涂层/金属界面剥离与膜下腐蚀交互作用[D]. 北京: 北京科技大学, 2022: 71-77.
HU W.Interaction of Coating/Metal Interfacial Debonding and Under-film Corrosion in UV/Salt Spray Coupling Environment[D]. Beijing: University of Science and Technology Beijing, 2022: 71-77.
[32] LI Y, GAO Z Y, WANG Q F, et al.Influence of Heat Treatment on Phase Distribution and Micro-Galvanic Corrosion in AZ91 and Mg-Gd-Y Alloys: A Comparative Analysis[J]. Journal of Alloys and Compounds, 2025, 1018: 179288.
[33] TAN W, GOU B Y, DING X D, et al.Wild Avalanches and Mild Fluctuations during Filiform Corrosion of Mg in NaCl Solution[J]. Physical Review Research, 2023, 5(3): 033219.
[34] 王宏新, 于锦, 宋影伟. 镁合金丝状腐蚀研究进展[J]. 表面技术, 2016, 45(12): 36-42.
WANG H X, YU J, SONG Y W.Research Progress of Filiform Corrosion on Magnesium Alloy[J]. Surface Technology, 2016, 45(12): 36-42.
[35] 莫格, 崔学军, 张颖君, 等. AZ31B镁合金表面微弧氧化/聚苯胺改性环氧涂层的腐蚀失效行为[J]. 中国表面工程, 2020, 33(2): 37-46.
MO G, CUI X J, ZHANG Y J, et al.Corrosion Failure Behavior of Micro-Arc Oxidation/Polyaniline Modified Epoxy Resin Coatings on AZ31B Mg Alloy[J]. China Surface Engineering, 2020, 33(2): 37-46.