熱浸鍍鋅鋁鎂(Zn-Al-Mg)鍍層鋼板因具有優異之耐蝕性能，近年來已廣泛應用於建築、汽車及戶外鋼構等領域。然而，材料長期暴露於高溫日照環境時，鍍層內部金屬間化合物可能因熱效應產生相變化，進而影響鍍層之腐蝕行為及耐蝕能力。因此，本研究以熱預算(Thermal Budget)概念，探討熱處理對不同鋁含量Zn-Al-Mg鍍層鋼板之相變化、微觀組織及腐蝕特性之影響。
本研究選用兩種商用熱浸鍍鋅鋁鎂鍍層鋼板，分別為ZAM(Zn-9Al-3Mg)及ZEXEED(Zn-19Al-6Mg)，經190°C、220°C及250°C熱處理1小時後，利用Pandat熱力學模擬軟體分析鍍層凝固路徑及相變化行為，並透過EBSD分析鍍層相組成、晶粒尺寸及晶體取向；再配合JASO M609-91循環腐蝕試驗(Cyclic Corrosion Test, CCT)模擬含氯大氣腐蝕環境。材料分析方面，利用OM、SEM、EDS、Mapping、Line Scan觀察鍍層表面與橫截面形貌，並結合XRD及FTIR分析不同腐蝕階段之腐蝕產物演變；最後配合開路電位(OCP)、循環伏安法(CV)、Tafel極化曲線及電化學阻抗頻譜(EIS)等電化學量測，探討熱處理前後鍍層之電化學腐蝕行為，並建立完整之腐蝕機制。
研究結果顯示，隨熱處理溫度提高，鍍層內MgZn2逐漸轉變為熱力學較穩定之Mg2Zn11，其中ZAM鍍層於250°C時相轉變最為明顯，而ZEXEED因具有較高Al含量，使MgZn2向Mg2Zn11之轉變受到抑制，顯示Al的多寡對Mg-Zn相變具有顯著影響。EBSD分析結果亦證實熱處理主要改變鍍層相組成，而晶粒尺寸變化有限，表示本研究之熱處理條件尚不足以造成明顯晶粒粗化。
腐蝕產物分析結果顯示，鍍層於循環腐蝕過程中主要依序生成ZnO、Simonkolleite(Zn5(OH)8Cl2·H2O)、Hydrozincite(Zn5(CO3)2(OH)6)、Zn-Al Layered Double Hydroxides(Zn-Al LDHs)及鐵系腐蝕產物(Fe2O3、FeO(OH))等。其中Al2O3與 Zn-Al LDHs可形成較緻密之保護層，有效延緩氯離子向鍍層內部擴散，提升鍍層耐 蝕能力。循環腐蝕試驗結果顯示，熱處理後各腐蝕階段皆有提前發生之趨勢，但ZEXEED鍍層於各腐蝕階段仍明顯晚於ZAM，顯示較高Al含量可有效維持鍍層保護能力。
電化學分析結果顯示，隨熱處理溫度提高，OCP逐漸負移，CV之氧化還原反應活性增加，Tafel極化曲線顯示腐蝕電流密度上升，而EIS分析結果則顯示膜電阻(Rf)與電荷轉移電阻(Rct)皆逐漸下降，CPE值增加，代表鍍層保護膜逐漸鬆散，腐蝕介質更容易穿透鍍層，使腐蝕反應加速。綜合材料分析及電化學結果可知，熱處理造成Mg-Zn相轉變會改變鍍層後續腐蝕行為，而提高Al含量可抑制MgZn2向Mg2Zn11之轉變，並促進Al2O3及Zn-Al LDHs等保護性腐蝕產物形成，因此ZEXEED鍍層整體耐蝕性能優於ZAM鍍層。本研究建立熱處理下Zn-Al-Mg鍍層相變化、腐蝕產物演變及電化學腐蝕行為之關聯，可作為Zn-Al-Mg鍍層材料設計、熱處理製程最佳化及高耐蝕鍍層開發之重要參考。

This study investigates the effects of heat treatment on the phase transformation and corrosion behavior of hot-dip Zn-Al-Mg alloy-coated steel sheets with different aluminum contents. Two commercial Zn-Al-Mg coatings, ZAM (Zn-9Al-3Mg) and ZEXEED (Zn-19Al-6Mg), were selected as the experimental materials. Heat treatments were conducted at 190°C, 220°C, and 250°C for 1 hour to simulate the long-term thermal exposure of coated steel sheets under sunlight based on the concept of thermal budget. The phase transformation behavior of the coatings was first analyzed using Pandat thermodynamic simulation software. Electron backscatter diffraction (EBSD) was then employed to characterize the phase distribution, crystallographic orientation, and grain size before and after heat treatment.
To evaluate the corrosion performance under atmospheric environments, cyclic corrosion testing (CCT) was conducted in accordance with the JASO M609-91 standard. Optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), elemental mapping, and line scan analyses were used to investigate the surface morphology, cross-sectional microstructure, elemental distribution, and intermetallic compound (IMC) evolution of the coatings. The corrosion products formed during different corrosion stages were identified using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Furthermore, electrochemical measurements, including open circuit potential (OCP), cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS), were performed to evaluate the corrosion resistance and electrochemical behavior of the coatings, and a comprehensive corrosion mechanism was established.
The results indicate that heat treatment promotes the phase transformation of Mg-Zn intermetallic compounds from MgZn2 to the thermodynamically stable Mg2Zn11. This transformation is more pronounced in the ZAM coating, whereas the higher aluminum content in ZEXEED suppresses the formation of Mg2Zn11. EBSD analysis further confirms that heat treatment significantly changes the phase fraction while exhibiting only a limited influence on grain size. XRD and FTIR analyses reveal that the corrosion products mainly evolve from ZnO, Simonkolleite (Zn5(OH)8Cl2·H2O), and Hydrozincite (Zn5(CO3)2(OH)6) during the early corrosion stage to Zn-Al layered double hydroxides (Zn-Al LDHs) and finally iron oxides during the later stages of corrosion. Among these corrosion products, Al2O3 and Zn-Al LDHs provide effective protection by retarding chloride ion penetration into the coating.
Electrochemical measurements demonstrate that increasing the heat-treatment temperature leads to a more negative open circuit potential, higher electrochemical activity, lower charge-transfer resistance, and a looser protective film, indicating an accelerated corrosion process. Nevertheless, owing to its higher aluminum content, the ZEXEED coating forms a denser protective layer consisting of Al2O3 and Zn-Al LDHs, resulting in superior corrosion resistance compared with the ZAM coating, even after heat treatment.
Overall, this study establishes the relationship between heat-treatment-induced phase transformation, corrosion product evolution, and electrochemical behavior of Zn-Al-Mg alloy coatings, providing valuable insights for optimizing heat-treatment processes and developing high-corrosion-resistant Zn-Al-Mg coated steel sheets.

1. Rosalbino, F., Angelini, E., Macciò, D., Saccone, A., & Delfino, S. (2007). Influence of rare earths addition on the corrosion behaviour of Zn–5% Al (Galfan) alloy in neutral aerated sodium sulphate solution. Electrochimica Acta, 52(24), 7107–7114.
2. Yu, Y., Shi, Q., Qiao, D., Du, X., Zhao, X., Wang, J., Zhang, G., & Peng, P. (2025). Effect of steel substrate roughness on microstructure and properties of hot-dip Zn-Al-Mg coating. Journal of Materials Research and Technology.
3. Yao, C., Tay, S. L., Zhu, T., Shang, H., & Gao, W. (2015). Effects of Mg content on microstructure and electrochemical properties of Zn–Al–Mg alloys. Journal of Alloys and Compounds, 645, 131–136.
4. Hammam, R. E., Abdel-Gawad, S. A., Moussa, M. E., Shoeib, M., & El-Hadad, S. (2023). Study of microstructure and corrosion behavior of cast Zn–Al–Mg alloys. International Journal of Metalcasting, 17(4), 2794–2807.
5. Kim, S.-H., Kim, S.-h., Kim, H.-M., Kang, J., Lee, M.-H., Oh, M.-S., & Yun, Y.-S. (2025). Enhancing the steam oxidation reactivity of Zn-Al-Mg alloy-coated steel sheets through heat treatment. Applied Surface Science, 702, 163329.
6. Xu, M., Zheng, Z., Han, D., Ma, R., Du, A., Fan, Y., Zhao, X., & Cao, X. (2023). Improvement of cracking resistance of hot-dip Zn-Al-Mg coatings by heat treatment. Materials Today Communications, 36, 106521.
7. Prosek, T., Hagström, J., Persson, D., Fuertes, N., Lindberg, F., Chocholatý, O., Taxén, C., Šerák, J., & Thierry, D. (2016). Effect of the microstructure of Zn-Al and Zn-Al-Mg model alloys on corrosion stability. Corrosion Science, 110, 71–81.
8. Diler, E., Rioual, S., Lescop, B., Thierry, D., & Rouvellou, B. (2012). Chemistry of corrosion products of Zn and MgZn pure phases under atmospheric conditions. Corrosion Science, 65, 178–186.
9. Mu, X., Jin, T., Xie, P., Yu, R., Hu, S., Li, B., Li, L., & Yuan, X. (2025). Organic coating failure and monitoring in atmospheric corrosion: from mechanisms to applications. Progress in Materials Science, 101592.
10. Prosek, T., Nazarov, A., Bexell, U., Thierry, D., & Serak, J. (2008). Corrosion mechanism of model zinc–magnesium alloys in atmospheric conditions. Corrosion Science, 50(8), 2216–2231.
11. Byun, J. M., Bang, S.-R., Kim, H. W., Kim, T.-Y., Hong, S.-J., & Do Kim, Y. (2017). Effect of heat treatment on corrosion resistance and adhesion property in Zn-Mg-Zn multi-layer coated steel prepared by PVD process. Surface and Coatings Technology, 309, 1010–1014.
12. 胡啟章. (2002). 電化學原理與方法. 五南圖書出版股份有限公司.
13. 施正雄. (2022). 儀器分析原理與應用. 五南圖書出版股份有限公司.
14. 林修正. (2005). 電化學科技辭典. 五南圖書出版股份有限公司.
15. Li, J.-p., Qiao, D.-g., Dong, S.-w., Peng, P., Yan, X.-t., & Zhang, X.-d. (2023). Analysis on phase selection and microstructure evolution in directionally solidified Zn-Al-Mg-Ce alloy. China Foundry, 20(4), 347–355.
16. Eddine Chaieb, H., Maurel, V., Ammar, K., Forest, S., Tanguy, A., Héripré, E., Nozahic, F., Mataigne, J.-M., & De Strycker, J. (2024). In-situ localization of damage in a Zn-Al-Mg coating deposited on steel by continuous hot-dip galvanizing. arXiv e-prints, arXiv: 2407.06148.
17. Liu, S., Hou, H., Shao, W., Yang, J., Wang, Z., Yang, Q., & LLorca, J. (2024). Revisiting the precipitation mechanisms of Guinier-Preston zones, η′, and η precipitates in Al-Zn-Mg alloys. Acta Materialia, 268, 119789.
18. Xu, C., Han, Y., Teng, H., Liu, H., Bai, X., & Shang, T. (2025). Application of CALPHAD Calculation in the Microstructure Design of the Industrial Zn-Al-Mg Coated Product. Journal of Phase Equilibria and Diffusion, 46(6), 553–567.
19. Xu, L., Cui, C., Lu, Q., Yang, H., & Zhang, W. (2023). Characterization of microstructural and corrosion behavior of cold sprayed Zn11Al3Mg alloy coating. Surface and Coatings Technology, 471, 129890.
20. Nishimura, K., Matsuda, K., Tsuchiya, T., Nunomura, N., Bendo, A., Isikawa, Y., Imai, K., Adachi, H., & Hutchison, W. D. (2019). Critical concentrations of Zn and Mg for enhanced diamagnetism in Al-Zn-Mg alloys. AIP Advances, 9(12).
21. Brennan, S., Bermudez, K., Kulkarni, N., & Sohn, Y. (2012). Diffusion couple investigation of the Mg-Zn system. In Magnesium Technology 2012 (pp. 323–327). Springer.
22. Ghatei-Kalashami, A., Khan, M. S., Lee, M.-Y., & Zhou, Y. N. (2022). High-temperature phase evolution of the ZnAlMg coating and its effect on mitigating liquid-metal-embrittlement cracking. Acta Materialia, 229, 117836.
23. Yao, C., Tay, S. L., Yang, J. H., Zhu, T., & Gao, W. (2014). Hot dipped zn-al-mg-cu coating with improved mechanical and anticorrosion properties. International Journal of Electrochemical Science, 9(12), 7083–7096.
24. Yan, D., He, J., Tian, B., Dong, Y., Li, X., Zhang, J., Xiao, L., & Jing, W. (2006). The corrosion behavior of plasma sprayed Fe2Al5 coating in molten Zn. Surface and Coatings Technology, 201(6), 2662–2666.
25. Khaliq, A., Alghamdi, A. S., Ramadan, M., Subhani, T., Rajhi, W., Haider, W., & Hasan, M. M. (2022). Intermetallic Compounds Formation during 316L Stainless Steel Reaction with Al-Zn-Si Coating Alloy. Crystals, 12(5), 735.
26. Ahiale, G. K., Javadinejad, H. R., Lee, M., Kim, H., & Kim, J. H. (2024). Microstructure and mechanical properties of ultrasonically welded aluminum to Zn–Mg–Al coated and uncoated mild steels. Journal of Materials Research and Technology, 33, 5102–5118.
27. Ho, C. Y., & Liao, G. H. (2025). Study of the Zn (xMg, yAl) coating on the phase distribution, electrochemical characteristics and simulated marine corrosion by the cycling corrosion test. Surfaces and Interfaces, 59, 105912.
28. 廖耿輝. (2024). 循環腐蝕試驗對不同鋁/鎂比例之熱浸鍍鋅鋁鎂鍍層鋼板之腐蝕行為研究與電化學分析
29. Hernández-Escobar, D., Rahman, Z. U., Yilmazer, H., Kawasaki, M., & Boehlert, C. J. (2019). Microstructural evolution and intermetallic formation in Zn-Mg hybrids processed by High-Pressure Torsion. Philosophical Magazine, 99(5), 557–584.
30. Zhang, T.-z. (2024). Structural, mechanical and electronic properties of precipitates in Mg− Zn alloys. Transactions of Nonferrous Metals Society of China, 34(8), 2507–2520.
31. Wang, Y., Chao, P., Moniri, S., Gao, J., Volkenandt, T., De Andrade, V., & Shahani, A. J. (2020). Integrated three-dimensional characterization of reactive phase formation and coarsening during isothermal annealing of metastable Zn–3Mg–4Al eutectic. Materials Characterization, 170, 110685.
32. Zhang, Z., Zhang, J., Zhao, X., Cheng, X., Liu, X., & Zhang, Q. (2024). Thermodynamic Simulation Calculations of Phase Transformations in Low-Aluminum Zn-Al-Mg Coatings. Materials 2024, 17, 2719. In.
33. Zeng, Q., Min, X., Luo, Z., Dai, H., & Liao, B. (2022). In-situ preparation of superhydrophobic Zn-Al layered double hydroxide coatings for corrosion protection of aluminum alloy. Materials Letters, 328, 133077.
34. Liu, Y., Gu, T., Liu, M., Wang, Z., Cao, G., Guo, Q., & Wang, C. (2024). Corrosion mechanism of a high corrosion-resistance Zn–Al–Mg coating in typical extremely harsh marine and cold environments. Journal of Materials Research and Technology, 33, 4290–4302.
35. Volovitch, P., Vu, T., Allély, C., Aal, A. A., & Ogle, K. (2011). Understanding corrosion via corrosion product characterization: II. Role of alloying elements in improving the corrosion resistance of Zn–Al–Mg coatings on steel. Corrosion Science, 53(8), 2437–2445.
36. He, X., Zhou, X., Shang, T., Liu, W., Jiang, G., Liu, C., Cheng, X., Zhang, X., & Li, X. (2024). Influence mechanism of different elements and alloy phases on the corrosion resistance of Zn-Al-Mg coated steel in the atmospheric environment: A review. Corrosion Communications, 13, 49–59.
37. Guo, J., He, Z., Zhang, Z., Wang, W., Xu, J., Chen, Z., Liu, T., & Guo, L. (2024). Influence of heat treatment on the microstructure evolution and corrosion performance of biodegradable Zn-Mg alloys. Materials Today Communications, 40, 109976.
38. Xiong, Z., Zhang, W., Wu, R., Ma, F., Wang, X., & Wang, G. (2024). One-step hydrothermal fabrication of Co-MOFs/LDH superhydrophobic composite coating with corrosion resistance and wear resistance on anodic aluminum oxide. Applied Surface Science, 677, 161023.
39. Bouramdane, Y., Haddad, M., Mazar, A., Aît Lyazidi, S., Oudghiri Hassani, H., & Boukir, A. (2024). Aged lignocellulose fibers of cedar wood (9th and 12th century): structural investigation using FTIR-deconvolution spectroscopy, X-ray diffraction (XRD), crystallinity indices, and morphological SEM analyses. Polymers, 16(23), 3334.
40. Persson, D., Wärnheim, A., Sainis, S., Lebozec, N., & Thierry, D. (2025). Atomic force infrared microscopy studies of SO2 induced atmospheric corrosion of ZnAlMg-coated steel in humid air. Vibrational Spectroscopy, 103883.
41. Diler, E., Rouvellou, B., Rioual, S., Lescop, B., Vien, G. N., & Thierry, D. (2014). Characterization of corrosion products of Zn and Zn–Mg–Al coated steel in a marine atmosphere. Corrosion Science, 87, 111–117.
42. Schürz, S., Luckeneder, G. H., Fleischanderl, M., Mack, P., Gsaller, H., Kneissl, A., & Mori, G. (2010). Chemistry of corrosion products on Zn–Al–Mg alloy coated steel. Corrosion Science, 52(10), 3271–3279.
43. Persson, D., Thierry, D., & LeBozec, N. (2023). The effect of microstructure on local corrosion product formation during initial SO2-induced atmospheric corrosion of ZnAlMg coating studied by FTIR-ATR FPA chemical imaging. Corrosion and Materials Degradation, 4(3), 503–515.
44. Na, Y., Pradhan, S. K., Kim, D.-G., Kim, S.-H., Yun, Y.-S., & Oh, M.-S. (2025). Electrochemical Evaluation of Corrosion Behavior and Product Characterization of Zn–Mg–Al Alloy-coated Steels in a Laboratory-simulated Full Immersion Marine Environment. Materials Today Communications, 114036.
45. Bucca, M., Dietzel, M., Tang, J., Leis, A., & Köhler, S. J. (2009). Nucleation and crystallization of otavite, witherite, calcite, strontianite, hydrozincite, and hydrocerussite by CO2 membrane diffusion technique. Chemical geology, 266(3-4), 143–156.
46. Zhang, S., He, X., Shang, T., Jiang, G., Liu, W., Teng, H., Chen, T., Cheng, X., & Liu, C. (2024). The initial corrosion mechanism of hot-dipping Zn–Al–Mg alloy coating in chloride-containing solution. Journal of Materials Science, 59(44), 20780–20795.
47. Nie, C., Cao, F., Zhu, T., Sun, Z., Wang, D., Wu, Y., & Ying, L. (2023). Study on the tribological properties and corrosion resistance of the in-situ grown Zn–Al-LDHs film on anodic aluminum surface. Materials Science and Engineering: B, 297, 116751.
48. He, Q.-Q., Zhou, M.-J., & Hu, J.-M. (2020). Electrodeposited Zn-Al layered double hydroxide films for corrosion protection of aluminum alloys. Electrochimica Acta, 355, 136796.
49. Yue, D., Tan, H., Hao, M., Wang, Z., Jia, Z., & He, C. (2026). In-Situ Growth of ZnMgAl-LDH Nanosheets in Anodic Alumina Pores: A Sustainable Strategy toward High-Performance Anticorrosion Coatings. Surfaces and Interfaces, 108615.
50. Guo, T., Wang, Y., Yu, L., Jin, Y., Zeng, B., Dou, B., Liu, X., & Lin, X. (2024). Roles of Al and Mg on the microstructure and corrosion resistance of zn-al-mg hot-dipped coated steel. Materials, 17(7), 1512.
51. Arabzadeh, H., Shahidi, M., & Foroughi, M. M. (2017). Electrodeposited polypyrrole coatings on mild steel: Modeling the EIS data with a new equivalent circuit and the influence of scan rate and cycle number on the corrosion protection. Journal of Electroanalytical Chemistry, 807, 162–173.
52. Rai, P. K., Rout, D., Satish Kumar, D., Sharma, S., & Balachandran, G. (2021). Effect of magnesium on corrosion behavior of hot-dip Zn-Al-Mg coating. Journal of Materials Engineering and Performance, 30(6), 4138–4147.