Electrochemical Evaluation of the Effect of Different NaCl Concentrations on Low Alloy- and Stainless Steels under Corrosion and Erosion-Corrosion Conditions

Corrosion and Materials Degradation Pub Date : 2022-02-19 DOI:10.3390/cmd3010006

F. Brownlie, T. Hodgkiess, A. Pearson, A. Galloway

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引用次数: 3

Abstract

The main objective of this study was to assess the influence of salt concentration on the corrosion behaviour, including the role of hydrodynamic conditions, of two broad classes of ferrous engineering materials. These are comprised of alloys, typified by a low-alloy steel (UNS G43400) that corrodes actively in aqueous conditions and a range of passive-film-forming stainless steels (UNS S31600, UNS S15500 and UNS S32760). Corrosion monitoring employed electrochemical (potentiodynamic polarisation) techniques. Three concentrations of aerated sodium chloride were utilised: 0.05 wt% NaCl, 3.5 wt% NaCl and 10 wt% NaCl. In quiescent, liquid impingement and solid/liquid impingement conditions, the corrosion rate of the low-alloy steel was observed to peak at 3.5 wt% NaCl, followed by a reduction in 10 wt% NaCl solution. These findings expand the range of previously reported trends, focused on static conditions. Such corrosion rate/salinity trends were observed to be dictated by the progress of the anodic reaction rather than influence on the cathodic reaction. Detailed studies were undertaken using segmented specimens to facilitate comparisons of the influence of hydrodynamic variations on corrosion behavior; these revealed that such variations influence the corrosion rates of low-alloy steel to a much lesser extent than the effect of changes in salinity. For the stainless steels, in quiescent and flowing conditions, when surface passive films are stable, there was a constant increase in corrosion rate with salinity. In solid-liquid conditions, however, the periodic film-destruction/repassivation events resulted in a similar corrosion rate/salinity trend to that displayed by the low-alloy steel, but with a much larger effect of hydrodynamic conditions. Additonally, the study revealed an underlying influence of stainless steel composition that mirrored, to an extent, the corrosion behaviour in pitting/re-passivation situations

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不同NaCl浓度对低合金和不锈钢在腐蚀和冲蚀条件下影响的电化学评价

本研究的主要目的是评估盐浓度对两大类含铁工程材料的腐蚀行为的影响，包括水动力条件的作用。这些由合金组成，典型的是低合金钢(UNS G43400)，在水条件下具有活性腐蚀，以及一系列被动成膜不锈钢(UNS S31600, UNS S15500和UNS S32760)。腐蚀监测采用电化学(动电位极化)技术。采用3种浓度的曝气氯化钠:0.05 wt% NaCl、3.5 wt% NaCl和10 wt% NaCl。在静态、液体撞击和固/液撞击条件下，低合金钢的腐蚀速率在3.5 wt% NaCl时达到峰值，随后在10 wt% NaCl溶液中降低。这些发现扩大了先前报道的趋势范围，主要集中在静态条件下。观察到这种腐蚀速率/盐度趋势是由阳极反应的进展决定的，而不是对阴极反应的影响。采用分段试样进行了详细的研究，以便比较水动力变化对腐蚀行为的影响;这些结果表明，这种变化对低合金钢腐蚀速率的影响程度远小于盐度变化的影响程度。对于不锈钢，在静态和流动条件下，当表面钝化膜稳定时，腐蚀速率随盐度的增加而不断增加。而在固液条件下，周期性的膜破坏/再钝化事件导致的腐蚀速率/盐度趋势与低合金钢相似，但水动力条件的影响要大得多。此外，研究还揭示了不锈钢成分的潜在影响，在一定程度上反映了点蚀/再钝化情况下的腐蚀行为

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来源期刊

Corrosion and Materials Degradation

CiteScore

4.50

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