Magnesium alloys, especially AZ31B, are widely used in the automotive, aerospace, and electronics industries due to their low density, high specific strength, and excellent electromagnetic shielding properties. However, their high chemical reactivity makes them highly susceptible to corrosion in humid or saline environments, significantly limiting their service life. Constructing superhydrophobic surfaces on magnesium alloys has emerged as an effective strategy to improve corrosion resistance by regulating surface roughness and surface energy at the solid-liquid-gas triple-phase interface, thereby isolating the material from corrosive media. This study proposes a synergistic surface modification approach that combines picosecond laser ablation with stearic acid chemical treatment to fabricate stable superhydrophobic layers on AZ31B magnesium alloy. This approach aims to enhance the alloy's corrosion resistance in harsh environments.
The primary objective of this research is to enhance the superhydrophobicity and corrosion resistance of AZ31B magnesium alloy surfaces by employing picosecond laser structuring followed by stearic acid modification. Initially, hierarchical micro/nanostructures are fabricated by picosecond laser ablation, with laser parameters such as power and scanning speed systematically adjusted to study their influence on the resulting surface morphology and wettability. In sub-optimal conditions concerning power and speed, the laser ablation spacing is varied between 20 μm and 150 μm to investigate its impact on surface topography and wettability. SEM and 3D profilometry analyses demonstrate that laser spacing is pivotal in micro/nanostructure formation. An optimal range of 40-100 μm facilitates the creation of desirable hierarchical structures, promoting the Cassie-Baxter wetting state by trapping air beneath water droplets and reducing solid-liquid contact. Notably, a spacing of 40 μm yields the best superhydrophobic performance with a maximum water contact angle of 150.07°. In contrast, a 20 μm spacing results in excessive surface roughness that compromises hydrophobicity, while a 150 μm spacing produces insufficient surface texture, thereby limiting air entrapment and reducing hydrophobic efficiency.
In addition, the laser-textured surfaces are chemically modified with stearic acid to reduce surface energy further and enhance hydrophobicity. The long hydrocarbon chains of stearic acid molecules are chemically adsorbed onto the surface of magnesium ions, forming a hydrophobic organic layer. EDS and XPS analyses confirm the successful attachment of stearic acid molecules. EDS results show increased carbon and oxygen contents and a corresponding decrease in magnesium content after modification. At the same time, XPS confirms the formation of magnesium stearate through chemical bonding between the carboxyl groups of stearic acid and surface magnesium ions. This chemical modification is vital in stabilizing the superhydrophobic surface by significantly reducing surface energy.
Electrochemical corrosion tests are performed on three samples: untreated, laser-treated only, and laser-treated, followed by stearic acid modification. The latter (Sample 2) exhibits the highest corrosion resistance, with a corrosion potential (Ecorr) of -1.428 4 V and a corrosion current density (Jcorr) of 5.952 8×10-5 A/cm², significantly outperforming the other samples. Due to the superhydrophobic surface, the enhanced corrosion resistance is attributed to the reduced interaction between the metal substrate and corrosive agents.
This study demonstrates that combining picosecond laser ablation and stearic acid modification effectively constructs a robust superhydrophobic structure on AZ31B magnesium alloy. The control of laser ablation spacing is critical for achieving ideal surface morphology that supports the Cassie-Baxter state. Meanwhile, stearic acid self-assembly contributes to long-term stability by reducing surface energy. Combining micro/nanostructure engineering and surface chemical modification has been identified as a promising solution for protecting magnesium alloys against corrosion in aggressive environments.
Key words
magnesium alloys /
laser ablation /
wetting model /
micro-nano structure /
superhydrophobicity
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References
[1] WU Z, LIU Y L, ZHANG Y, et al.The Effect of Micro/Nanostructures Formed by Laser Ablation on the Superhydrophobicity of AZ31B Magnesium Alloy[J]. Journal of Materials Research, 2024, 39(5): 850-863.
[2] ZHANG S L, JIANG J, ZOU X R, et al.Progress of Laser Surface Treatment on Magnesium Alloy[J]. Frontiers in Chemistry, 2022, 10: 999630.
[3] WANG J X, ZOU Y, DANG C, et al.Research Progress and the Prospect of Damping Magnesium Alloys[J]. Materials, 2024, 17(6): 1285.
[4] XIONG J, WANG R C, ZHAO D Q, et al.Effects of Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of Automatic Laser-Arc Hybrid Welded AZ31B Magnesium Alloys[J]. Metals, 2024, 14(7): 806.
[5] LITROP A, KLEMENC J, NAGODE M, et al.Enhanced Cyclically Stable Plasticity Model for Multiaxial Behaviour of Magnesium Alloy AZ31 under Low-Cycle Fatigue Conditions[J]. Materials, 2024, 17(18): 4659.
[6] CHINO Y, MABUCHI M, KISHIHARA R, et al.Mechanical Properties and Press Formability at Room Temperature of AZ31 Mg Alloy Processed by Single Roller Drive Rolling[J]. Materials Transactions, 2002, 43(10): 2554-2560.
[7] AHMADI M, TABARY S A A B, RAHMATABADI D, et al. Review of Selective Laser Melting of Magnesium Alloys: Advantages, Microstructure and Mechanical Characterizations, Defects, Challenges, and Applications[J]. Journal of Materials Research and Technology, 2022, 19: 1537-1562.
[8] ZHANG Y, ZHANG Z T, YANG J L, et al.A Review of Recent Advances in Superhydrophobic Surfaces and Their Applications in Drag Reduction and Heat Transfer[J]. Nanomaterials, 2022, 12(1): 44.
[9] GU R, SHEN J, HAO Q, et al.Harnessing Superhydrophobic Coatings for Enhancing the Surface Corrosion Resistance of Magnesium Alloys[J]. Journal of Materials Chemistry B, 2021, 9(48): 9893-9899.
[10] GUO F Q, DUAN S W, WU D T, et al.Facile Etching Fabrication of Superhydrophobic 7055 Aluminum Alloy Surface towards Chloride Environment Anticorrosion[J]. Corrosion Science, 2021, 182: 109262.
[11] NISHIMOTO S, BHUSHAN B.Bioinspired Self- Cleaning Surfaces with Superhydrophobicity, Superoleophobicity, and Superhydrophilicity[J]. RSC Advances, 2013, 3(3): 671-690.
[12] 龙江游, 吴颖超, 龚鼎为, 等. 飞秒激光制备超疏水铜表面及其抗结冰性能[J]. 中国激光, 2015, 42(7): 164-171.
LONG J Y, WU Y C, GONG D W, et al.Femtosecond Laser Fabricated Superhydrophobic Copper Surfaces and Their Anti-Icing Properties[J]. Chinese Journal of Lasers, 2015, 42(7): 164-171.
[13] CHU W S, SHEHROZE M M, TRAN N G, et al.Green Fabrication of Superhydrophobic Surfaces Using Laser Surface Texturing without Toxic Chemicals: A Review[J]. International Journal of Precision Engineering and Manufacturing, 2024, 25(5): 1101-1123.
[14] SUN K, YANG H, XUE W, et al.Anti-Biofouling Superhydrophobic Surface Fabricated by Picosecond Laser Texturing of Stainless Steel[J]. Applied Surface Science, 2018, 436: 263-267.
[15] XUE C H, JIA S T, ZHANG J, et al. Large-Area Fabrication of Superhydrophobic Surfaces for Practical Applications: An Overview[J]. Science and Technology of Advanced Materials, 2010, 11(3)033002.
[16] NOSONOVSKY M, BHUSHAN B.Superhydrophobic Surfaces and Emerging Applications: Non-Adhesion, Energy, Green Engineering[J]. Current Opinion in Colloid & Interface Science, 2009, 14(4): 270-280.
[17] BOROVIKOV S S.Study of the Droplet Transition from Cassie to Wenzel State on Laser-Modified Metal Surfaces[J]. Journal of Physics: Conference Series, 2022, 2211(1): 012007.
[18] NGO C V, LIU Y, LI W, et al.Scalable Wettability Modification of Aluminum Surface through Single-Shot Nanosecond Laser Processing[J]. Nanomaterials, 2023, 13(8): 1392.
[19] RUZANKINA J, VASILIEV O, TARASOV S.Investigation of Functional Properties of Metal Surfaces after Laser Treatment[J]. Journal of Physics: Conference Series, 2019, 1410(1): 012171.
[20] ZHU D Y, LIU Q, LI Q.Fabrication of Superhydrophobic, Permeable, and Anti-Reflective Porous Steel Surfaces Using Laser Ablation and Heat Treatment[J]. The International Journal of Advanced Manufacturing Technology, 2024, 132(11): 5695-5703.
[21] CHEN K S, LIU H W, WU R M, et al.Femtosecond Laser-Induced Hierarchical Micro/Nanostructures of Stainless-Steel Mesh for Oil-Water Separation and Detection of High Concentration Hydrogen[J]. Optics & Laser Technology, 2025, 181: 111981.
[22] THENNAKOON C A, RAJAPAKSHE R B S D, MALIKARAMAGE A U, et al. Factors Affecting the Hydrophobic Property of Stearic Acid Self-Assembled on the TiO2 Substrate[J]. ACS Omega, 2022, 7(51): 48184-48191.
[23] PERTAYS K M, THOMPSON G E, ALEXANDER M R.Self-Assembly of Stearic Acid on Aluminium: The Importance of Oxide Surface Chemistry[J]. Surface and Interface Analysis, 2004, 36(10): 1361-1366.
[24] TANG Y P, CAI Y K, WANG L, et al.Formation Mechanism of Superhydrophobicity of Stainless Steel by Laser-Assisted Decomposition of Stearic Acid and Its Corrosion Resistance[J]. Optics & Laser Technology, 2022, 153: 108190.
[25] WEI Z B, JIANG D Y, CHEN J, et al.Fabrication of Mechanically Robust Superhydrophobic Aluminum Surface by Acid Etching and Stearic Acid Modification[J]. Journal of Adhesion Science and Technology, 2017, 31(21): 2380-2397.
[26] XU W, RAJAN K, CHEN X G, et al.Facile Electrodeposition of Superhydrophobic Aluminum Stearate Thin Films on Copper Substrates for Active Corrosion Protection[J]. Surface and Coatings Technology, 2019, 364: 406-415.
[27] MEHMOOD U, AL-SULAIMAN F A, YILBAS B S, et al. Superhydrophobic Surfaces with Antireflection Properties for Solar Applications: A Critical Review[J]. Solar Energy Materials and Solar Cells, 2016, 157: 604-623.
[28] HUANG F, MOTEALLEH B, WANG D H, et al.Tailoring Intrinsic Hydrophobicity and Surface Energy on Rough Surface via Low-T Cassie-Wenzel Wetting Transition Method[J]. AIChE Journal, 2023, 69(3): e17908.
Funding
Provincial Science and Technology Innovation Special Funds in Yangjiang City (SDZX2023004); Research and Promotion Application of Laser Processing Technology for Hardware Knives and Scissors in Yangjiang
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