The Kinetics of Chloride-Induced Filiform Corrosion on Aluminum Alloy AA2024-T3

The Kinetics of Chloride-Induced Filiform Corrosion on Aluminum Alloy AA2024-T3
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铝合金 AA2024-T3 氯化物丝状腐蚀动力学

DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
H. McMurray
H. McMurray
中科院分区：
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文献类型：
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作者：
Geraint Williams;H. McMurray

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使用扫描开尔文探针 (SKP) 研究聚乙烯醇缩丁醛涂层 AA2024-T3 铝合金上发生丝状腐蚀 (FFC) 的动力学和机理。为了控制进入灯丝头群的电解液量，FFC 是通过将一定量的 HCl 水溶液直接注入渗透性涂层缺陷来启动的。随后，通过在 20°C 和 93% 相对湿度下对固定样品区域进行重复原位扫描，获得随时间变化的自由腐蚀电位 (E corr ) 图。引发过程中引入的 HCl (N HCl ) 摩尔数会系统地变化，并分析所得的 E corr 分布，以提供有关灯丝尺寸和 FFC 传播速率的详细信息。导出了将各个灯丝头电解质液滴的体积与灯丝头半径联系起来的方程。还导出了将总（总体）灯丝头电解质体积与 N HCl 相关的方程。利用这些关系推导出一系列动力学方程，预测在涂层分层速率由表面控制或由膜下离子迁移控制的情况下单个细丝和细丝群体的传播速率。与实验动力学的比较表明，对于所研究的系统，涂层分层速率是表面控制的，即与灯丝头电解质液滴和金属基底之间存在的界面面积成正比。
A scanning Kelvin probe (SKP) is used to study the kinetics and mechanism of filiform corrosion (FFC) as it occurs on polyvinyl butyral-coated AA2024-T3 aluminum alloy. In order to control the quantity of electrolyte entering the filament-head population, FFC is initiated by injecting a measured quantity of aqueous HCl directly into a penetrative coating defect. Subsequently, time-dependent free corrosion potential (E corr ) maps are obtained by repeated in situ scanning of a fixed sample area at 20°C and 93% relative humidity. The number of moles of HCl (N HCl ) introduced during initiation is varied systematically and the resulting E corr distributions analyzed to provide detailed information on filament dimensions and FFC propagation rates. Equations are derived relating the volume of individual filament-head electrolyte droplets to filament-head radius. Equations are also derived relating the total (population) filament-head electrolyte volume to N HCl . Using these relationships a series of kinetic equations are derived predicting propagation rates for individual filaments and filament populations under circumstances where rates of coating delamination are surface controlled or controlled by underfilm ion migration. Comparison with experimental kinetics shows that for the system studied the rate of coating delamination is surface controlled, i.e., proportional to the interfacial area existing between the filament-head electrolyte droplet and the metal substrate.