Abstract
The passivation of Ni-22Cr, Ni-22Cr-6Mo, and Ni-22Cr-6Mo-3W (wt%) was characterized from 100 s to 10 days in 0.1 M NaCl in pH 4 at various potentials in the passive range. The influence of aqueous solution exposure time in NaCl (exposure aging), passivation potential, as well as Ni-Cr-X alloy composition (Mo or W) on passive film growth, composition, oxidation state, molecular identity, and inner versus outer film layering were investigated. Initial passive film formation was dominated by Ni(II). Cr(III) oxides and hydroxides tended to enrich upon formation and exposure aging. Corundum and rock salt are speculated to undergo a solid-state phase transformation to form NiCr2O4 at long times under certain conditions. The concept of the time-potential-transformation diagrams to describe the evolution of passive film phases and protectiveness is introduced. Factors limiting Cr(III) enrichment were discussed. Aliovalent Mo and W ions were detected in passive films, particularly after aging. The roles of Cr enrichment, Ni depletion, and Mo and/or W aliovalent cations after oxide aging towards protectiveness to passive and localized corrosion in chloride (Cl-) solutions were discussed.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
