Effect of the crevice gap on the initiation of crevice corrosion in passive metals
Effect of the crevice gap on the initiation of crevice corrosion in passive metals
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DOI：
10.5006/1.3287850
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发表时间：
2004-08-01
期刊：
影响因子：
1.6
通讯作者：
Postlethwaite, J
中科院分区：
文献类型：
--
作者：
Heppner, KL;Evitts, RW;Postlethwaite, J
过去对控制被动金属缝隙的活跃缝隙腐蚀时间(潜伏期)的机制的研究已经产生了与B点模型、德拜-休克尔极限定律和其他活度模型相结合的理论模型，以修正中等浓度下的非理想行为。在这项研究中，Watson和Postlethwaite的输运模型与Pitzer的离子相互作用模型相耦合，以预测缝隙对Ir液滴和缝隙溶液化学活性的影响。提出了缝隙外氧还原和缝隙内氢离子还原两种阴极反应来平衡金属的溶解。为了验证模型的有效性，模拟了Alavi和Cottis的实验型304(UNS S30400)不锈钢缝隙。模型预测在过去模型预测的基础上有所改进，并在实验不确定度内与本实验工作的观测结果相匹配。还预测了缝隙对浸泡在25℃的0.5M氯化钠溶液中的钛缝隙的影响。随着缝隙的减小，溶液的红外降、电导率和化学活性增加。研究了Ir下降与溶液电荷中性度偏差的关系。
Past research into the mechanism governing the time to active crevice corrosion-the incubation period-of a passive metal crevice has produced theoretical models coupled with the B-dot model, the Debye-Huckel limiting law, and other activity models to correct for nonideal behavior at moderately high concentrations. In this research, the transport model of Watson and Postlethwaite is coupled with the ionic interaction model of Pitzer to predict the effect of the crevice gap on the iR drop and chemical activity of the crevice solution. Two cathodic reactions, crevice external oxygen reduction and crevice internal hydrogen ion reduction, are assumed to balance metal dissolution. To validate the model, the experimental Type 304 (UNS S30400) stainless steel crevice of Alavi and Cottis is simulated. Model predictions improve upon predictions of past models and match observations of this experimental work within experimental uncertainty. The effect of crevice gap on a titanium crevice immersed in 0.5 M aqueous sodium chloride (NaCl) solution at 25 degreesC also is predicted. The iR drop, electrical conductivity, and chemical activity of the solution increases as the crevice gap decreases. The relationship between iR drop and deviation from charge electroneutrality of the solution is investigated.