水性高铝Al-Zn-Mg-Si涂层在海水中腐蚀产物形成及腐蚀机制

In view of the failure of the protective coating of steel structure in marine corrosive environment, this project intends to develop novel water-based Al-Zn-Mg-Si alloy coating technologies with long-life and low temperature solidified by making the flake powders out of hot-dip galvanized alloy with high Al content (Al≥55%). Electrochemical tests and physical analysis will be used to investigate the influence of the coating compositions on the corrosion behavior and the nature of corrosion products of Al-Zn-Mg-Si coatings in seawater. Moreover, the synergetic effect of the main protective mechanisms of Al-Zn-Mg-Si alloy coating will be studied, and then the influence of different compositions on corrosion mechanism of coatings will be revealed, followingly, the relationship between the corrosion mechanism and the life of the coatings will be also explored. In addition, the evolution of morphologies and compositions of corrosion products will be revealed, the formation kinetics of the corrosion products will be explored, and finally to establish the related models. The action mechanism of the alloying elements such as Mg, Al, Si and so on will be researched emphatically, and the formation conditions of amorphous/nanocrystalline corrosion products will be proposed. The semiconducting properties of the corrosion product film will be studied based on the Mott-Schottky theory, and the transport kinetics of the corrosive ions in the film will be explored, to elucidate the damage mechanism of the corrosion product film, and the building of predict model of the remaining life for the coating based on the ion diffusion kinetics. This project will provide a scientific basis and an effective countermeasure to solve the long-term protection of steel structure in maritime climate.

针对海洋腐蚀环境中钢结构防护涂层的失效问题，本项目拟将高铝（Al≥55%）热浸镀合金制成鳞片粉，发展长寿命低温固化耐海水腐蚀的水性高铝Al-Zn-Mg-Si合金涂层技术。综合运用电化学测试和物理分析手段研究成分特征对涂层在海水中的腐蚀行为和腐蚀产物膜性质的影响规律，探索涂层主要防护机制间的协同作用，揭示成分特征对腐蚀机制的影响规律，进而建立涂层腐蚀机理与涂层寿命的关系；通过揭示优化涂层腐蚀产物的结构组成演化规律，探索腐蚀产物膜的形成动力学，并构建相关模型，重点研究Mg、Al、Si等合金元素的作用机理，提出非晶/纳米晶腐蚀产物的形成条件。利用Mott-Schottky理论研究腐蚀产物膜的半导体性质，探究膜内腐蚀性离子的传输动力学，阐明腐蚀产物膜的破损机理，基于离子扩散动力学建立涂层剩余寿命预测模型。本项目的实施为解决钢结构在海洋性气候的长效防护问题提供科学依据和有效的防护对策。

针对海洋腐蚀环境中钢结构防护涂层的失效问题，本项目将高铝（Al≥55%）热浸镀合金制成鳞片粉，发展长寿命低温固化耐海水腐蚀的水性高铝Al-Zn-Mg-Si合金涂层技术。综合运用电化学测试和物理分析手段研究成分特征对涂层在海水中的腐蚀行为和腐蚀产物膜性质的影响规律，揭示成分特征对腐蚀机制的影响规律；通过揭示优化涂层腐蚀产物的结构组成演化规律，探索腐蚀产物膜的形成和破坏动力学过程，建立等效电路模型，并提出非晶/纳米晶腐蚀产物的形成机理和条件。结果表明，优化涂层(55~69.78)Al-(24.64~40)Zn-3.4Mg-1.6 Si粉涂层腐蚀过程经历活化腐蚀、腐蚀产物的自修复和屏蔽阶段和涂层对基体的阴极保护三个阶段，其中非晶腐蚀产物膜屏蔽作用机制起主要作用，腐蚀产物层内晶粒较长期维持纳米级/非晶状态，对涂层产生自修复作用和屏蔽作用，限制腐蚀性粒子向涂层基体界面的传输，减缓金属粉消耗速率，显著延长涂层寿命。非晶腐蚀产物成分主要为锌铝碱式碳酸盐（简称Zn-Al LDH)和镁铝碱式碳酸盐(简称Mg-Al LDH)。微米级Al-Zn-Mg-Si粉涂层微观尺度成分均匀，涂层腐蚀过程形成的扩散控制的腐蚀产物（logI-logt直线斜率k=−0.5），能够满足阴极保护与腐蚀产物屏蔽作用机制的优化配合，最大程度的发挥涂层性能。