Cr, Mo and W alloying additions in Ni and their effect on passivity

Lloyd, A. C.; Noël, James J.; McIntyre, Susan; Shoesmith, David W.

doi:10.1016/j.electacta.2004.01.061

Cited by 221 publications

(140 citation statements)

References 30 publications

Supporting

Mentioning

120

Contrasting

Unclassified

Order By: Relevance

“…It is possible that Lloyd et al [9] detected metallic Ni in the underlying alloy below the thin air formed oxide layer, this would be consistent with their SIMS observation of Ni enrichment at the alloy surface. No published work on compositional analysis of passive films on HVOF sprayed Inconel 625 has been found.…”

Section: Introductionsupporting

confidence: 60%

See 1 more Smart Citation

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Bakare

Voisey

Roe

et al. 2010

Applied Surface Science

View full text Add to dashboard Cite

There is a well known performance gap in corrosion resistance between thermally sprayed corrosion resistant coatings and the equivalent bulk materials. Interconnected porosity has an important and well known effect, however there are additional relevant microstructural effects. Previous work has shown that a compositional difference exists between the regions of resolidified and non-melted material that exist in the as-sprayed coatings. The resolidified regions are depleted in oxide forming elements due to formation of oxides during coating deposition. Formation of galvanic cells between these different regions is believed to decrease the corrosion resistance of the coating. In order to increase understanding of the details of this effect, this work uses X-ray photoelectron spectroscopy (XPS) to study the passive films formed on thermally sprayed coatings (HVOF) and bulk Inconel 625, a commercially available corrosion resistant Ni-Cr-Mo-Nb alloy. Passive films produced by potentiodynamic scanning to 400mV in 0.5M sulphuric acid were compared with air formed films. The poorer corrosion performance of the thermally sprayed coatings was attributed to Ni(OH) 2 , which forms a loose, non-adherent and therefore non-protective film. The good corrosion resistance of wrought Inconel 625 is due to formation of Cr, Mo and Nb oxides.

show abstract

Section: Introductionsupporting

confidence: 60%

“…The work presented in this paper considers air grown films, these are significantly thinner with typical thicknesses of a few nanometers [9]. Lloyd et al [9] report the presence of NiO, Cr 2 O 3 and MoO 3 in the air formed film on Inconel 625.…”

Section: Introductionmentioning

confidence: 96%

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Bakare

Voisey

Roe

et al. 2010

Applied Surface Science

View full text Add to dashboard Cite

show abstract

“…The surface films' compositions formed in this work are largely consistent with those observed by Lloyd et al who have reported XPS analyses of passive films formed on alloy 625 and other Ni-Cr-Mo alloys in de-aerated 0.1 M NaCl and 0.1 M H 2 SO 4 at various temperatures. [11] While their results are presented in terms of oxide concentrations (NiO at% for example), they are qualitatively similar to those found here for both the native oxide and the oxide formed in de-aerated solution. It should be noted, however, that the potentials used in the work by Lloyd et al were significantly more anodic than those used here (>0.4 V SHE).…”

Section: Open Circuit Measurementssupporting

confidence: 80%

Passive and transpassive films formed on a nickel alloy in ammoniacal solution

Asselin

Alfantazi

Rogak

2009

Surface & Interface Analysis

View full text Add to dashboard Cite

The surface of alloy 625 (Ni-22Cr-9Mo) was characterized with XPS and AES depth profiling after exposure to mildly alkaline ammoniacal solution at open circuit and after potentiostatic treatments at various potentials. It was determined that the passive surface film was a Cr and Mo oxide that was depleted in Ni with respect to the bulk alloy. Increased solution temperatures or oxygen concentrations decreased the Ni to Cr ratio in the passive film. The alloy's transpassive film was characterized using SEM and EDX as well as XPS. The transpassive film was heavily depleted in Ni and Cr and consisted mainly of an oxide of Fe.

show abstract

“…It has been demonstrated previously [41][42][43] that the PDM can readily explain the observations of the passive state on Alloy-22. Characterization work 41,[44][45][46] has demonstrated that the passive film on Alloy-22 has a distinct layered structure with the inner layer primarily comprising Cr(III) oxide, so it is assumed in the optimization that point defective Cr 2 O 3 is the principal composition of the barrier layer. Fig.…”

Section: Results and Analysis By Numerical Optimizationmentioning

confidence: 99%

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

Lü

Engelhardt

Kursten

et al. 2016

J. Electrochem. Soc.

View full text Add to dashboard Cite

The theory of the kinetics of metastable pit nucleation in terms of the Point Defect Model (PDM) has been applied the first time to describing the evolution of the nucleation rate of metastable pits on a variety of metallic substrates. The PDM successfully accounts for the experimental data that have been reported in the literature on stainless steel, carbon steel, iron, aluminum, and Alloy-22, and which are judged to be reliable and reproducible. Important fundamental parameters related to metastable pitting such as total number density of pitting nucleation sites, dissolution time of the cap over the pit, energy related to absorption of the aggressive ions into oxygen vacancies in the surface of the barrier layer, vacancy condensation rate, and the time at which the nucleation rate of metastable pits is maximum were obtained from the optimization of the PDM on the experimental data, as reported in the present paper. The values obtained for those parameters are in good agreement with values and observations reported elsewhere. The present work successfully demonstrates the capacity of the PDM in accounting for experimental observations of metastable pitting and that the PDM can be applied as an underlying theory for studying and understanding metastable pitting on metal surfaces. The passive state is not perfectly protective and passivity breakdown occurs for various reasons, giving rise to enhanced general corrosion rate or to localized corrosion. Localized passivity breakdown is especially of great concern, because it results in the nucleation and propagation of pits and the subsequent nucleation and growth of cracks provided that there is sufficient tensile stress in the system to initiate crack nucleation at the stress raiser represented by the pit. Metastable pitting, in which passivity breakdown occurs followed immediately by repassivation, is now well-accepted as being an integral part of the process of pitting corrosion on a metal or alloy, culminating in the accumulation of damage via the development of stable pits. It is also well-recognized that repassivation reflects the failure on the part of the pit nucleus to establish a spatial separation between the local cathode and the local anode with the former occurring on the external surfaces and the latter taking place in the nucleus, which is necessary for the buildup and maintenance of the aggressive conditions of high [Cl − ] and high [H + ] (low pH) that cause the pits to grow as stable pits, until they, too, die via delayed repassivation (due to the inability of the pit to maintain separation of the local cathode and the local anode, because of the limited availability of resources of the cathodic depolarizer on the external surfaces).Numerous authors have reported metastable pit nucleation rate data measured under more-or-less well-defined conditions. Williams et al.1-3 reported a good proportional correspondence for Type 304L SS between the nucleation frequency of metastable pits and the frequency of occurrence of propagating (stable) pits, that ...

show abstract

Cr, Mo and W alloying additions in Ni and their effect on passivity

Cited by 221 publications

References 30 publications

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

Passive and transpassive films formed on a nickel alloy in ammoniacal solution

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

Contact Info

Product

Resources

About