{"title":"Molybdenum effects on the stability of passive films unraveled at the nanometer and atomic scales","authors":"Vincent Maurice, Philippe Marcus","doi":"10.1038/s41529-023-00418-6","DOIUrl":null,"url":null,"abstract":"Data recently obtained on model FeCrNi(Mo), 316 L stainless steel, and FeCrNiCo(Mo) passivated surfaces by advanced surface analysis and density functional theory modeling are comprehensively discussed to unravel the multiple effects that molybdenum might have at the nanometer and atomic scales to enhance the stability of passive films. The key role played on corrosion protection by the compositional and structural nanoscale defects of the passive film that originate from the pre-passivation mechanisms of the surface is considered. It is shown how Mo, enriched together with Cr in the nanometer-thick passive film, can combine several effects to enhance the resistance to Cl--induced passivity breakdown. Enriched as Mo(VI) species in the outer exchange layer of the passive film, Mo impedes the deep penetration of Cl- ions and limits their access to the inner barrier layer. Dispersed as Mo(IV) at the interface with the inner layer, Mo protects against the entry of Cl- ions into the defect sites of the Cr(III) oxide barrier. Present as Mo(IV + δ) in the Fe-rich compositional nanoscale defects self-generated by the local failure of Cr supply upon initial formation of the barrier layer, Mo enhances the selective dissolution of iron and its replacement by chromium and molybdenum. By impeding the formation of O vacancies, Mo also increases the resistance against chloride entry in the oxide matrix, thereby curing these the Fe-rich weak sites against Cl--induced passivity breakdown.","PeriodicalId":19270,"journal":{"name":"npj Materials Degradation","volume":null,"pages":null},"PeriodicalIF":6.6000,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41529-023-00418-6.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"npj Materials Degradation","FirstCategoryId":"88","ListUrlMain":"https://www.nature.com/articles/s41529-023-00418-6","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Data recently obtained on model FeCrNi(Mo), 316 L stainless steel, and FeCrNiCo(Mo) passivated surfaces by advanced surface analysis and density functional theory modeling are comprehensively discussed to unravel the multiple effects that molybdenum might have at the nanometer and atomic scales to enhance the stability of passive films. The key role played on corrosion protection by the compositional and structural nanoscale defects of the passive film that originate from the pre-passivation mechanisms of the surface is considered. It is shown how Mo, enriched together with Cr in the nanometer-thick passive film, can combine several effects to enhance the resistance to Cl--induced passivity breakdown. Enriched as Mo(VI) species in the outer exchange layer of the passive film, Mo impedes the deep penetration of Cl- ions and limits their access to the inner barrier layer. Dispersed as Mo(IV) at the interface with the inner layer, Mo protects against the entry of Cl- ions into the defect sites of the Cr(III) oxide barrier. Present as Mo(IV + δ) in the Fe-rich compositional nanoscale defects self-generated by the local failure of Cr supply upon initial formation of the barrier layer, Mo enhances the selective dissolution of iron and its replacement by chromium and molybdenum. By impeding the formation of O vacancies, Mo also increases the resistance against chloride entry in the oxide matrix, thereby curing these the Fe-rich weak sites against Cl--induced passivity breakdown.
期刊介绍:
npj Materials Degradation considers basic and applied research that explores all aspects of the degradation of metallic and non-metallic materials. The journal broadly defines ‘materials degradation’ as a reduction in the ability of a material to perform its task in-service as a result of environmental exposure.
The journal covers a broad range of topics including but not limited to:
-Degradation of metals, glasses, minerals, polymers, ceramics, cements and composites in natural and engineered environments, as a result of various stimuli
-Computational and experimental studies of degradation mechanisms and kinetics
-Characterization of degradation by traditional and emerging techniques
-New approaches and technologies for enhancing resistance to degradation
-Inspection and monitoring techniques for materials in-service, such as sensing technologies