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Title: CONSIDERATIONS OF THE ROLE OF THE CATHODIC REGION IN LOCALIZED CORROSION

Authors:
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
882576
Report Number(s):
NA
MOL.20051219.0024 DC#46315
Resource Type:
Conference
Resource Relation:
Journal Name: n/a; Conference: n/a
Country of Publication:
United States
Language:
English

Citation Formats

KELLY, R.G., LANDAU, U., PAYER, J.H.. CONSIDERATIONS OF THE ROLE OF THE CATHODIC REGION IN LOCALIZED CORROSION. United States: N. p., 2005. Web.
KELLY, R.G., LANDAU, U., PAYER, J.H.. CONSIDERATIONS OF THE ROLE OF THE CATHODIC REGION IN LOCALIZED CORROSION. United States.
KELLY, R.G., LANDAU, U., PAYER, J.H.. Mon . "CONSIDERATIONS OF THE ROLE OF THE CATHODIC REGION IN LOCALIZED CORROSION". United States. doi:. https://www.osti.gov/servlets/purl/882576.
@article{osti_882576,
title = {CONSIDERATIONS OF THE ROLE OF THE CATHODIC REGION IN LOCALIZED CORROSION},
author = {KELLY, R.G., LANDAU, U., PAYER, J.H.},
abstractNote = {},
doi = {},
journal = {n/a},
number = ,
volume = ,
place = {United States},
year = {Mon Dec 19 00:00:00 EST 2005},
month = {Mon Dec 19 00:00:00 EST 2005}
}

Conference:
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  • No abstract prepared.
  • The ability of wetted cathodes of limited area to support localized corrosion sites on passive materials exposed to atmospheric conditions was studied computationally. The analysis pertains to conditions where metal surfaces are covered by thin layers of moisture in contrast to conditions of full immersion. The moisture may be a continuous layer or in patches with and without particulate on the surface. These conditions are of interest for the surfaces of the waste packages at the proposed Yucca Mountain Repository where waste packages are supported in air. The cathode capacity was characterized by the total net cathodic current, I{sub net},more » which the surface surrounding a localized corrosion site (i.e., a pit or crevice) could supply. The cathode capacity increases with increasing cathode area, but it saturates at finite cathode sizes due to the resistance of the thin electrolyte layer. The magnitude of the capacity depends on the water layer thickness, the solution conductivity, and the electrochemical reaction kinetics. The presence of particulates is treated by considering both volume and surface coverage effects. The limited electrolyte volume under thin film conditions can lead to rapid pH changes which decrease the cathode capacity due to the slower electrochemical kinetics at elevated pH. These effects can make localized corrosion less likely to be sustained.« less
  • A comparison of a spectral analysis using the fast Fourier transform (FFT) and the maximum entropy method (MEM) was carried out in the case in which both methods can be performed, that is, when several time acquisitions can be recorded. A summary of the principles of the MEM is given. Then the main properties of this method are investigated, that is, influence of the MEM order on the spectrum accuracy, validity of the low-frequency plateau usually given by this technique, overlapping of spectra measured for different frequency bandwidths, and influence of a slow evolution of the amplitude of the signalmore » fluctuations. The susceptibility to pitting corrosion of type 304 stainless steel and type 304 modified by molybdenum (Mo) by means of ion implantation was studied. The power spectral densities (PSD) measured with the FFT and MEM techniques are in reasonable agreement, except for low electrochemical current noises (ECN) buried in the parasitic noise generated by the power supply. In that case, the FFT technique is more appropriate than the MEM, which gave qualitative results only. The type 304 stainless steel showed a large metastable pitting leading to only a few macroscopic pits, whereas the type 304 Mo-implanted specimen showed a very low metastable pitting leading to many hemispheric pits covered by the Mo-implanted layer, under which localized corrosion occurred.« less
  • The initial development and growth of defects from engineered surfaces, i.e. fine abraded, polished, shot peened etc., often dominates the resulting component lifetime, particularly for materials of high strength and limited ductility. When subject to the conjoint action of stress and environment this lifetime is impaired and reductions in fatigue strength are often observed resulting from a reduction in defect development time, often termed initiation, and enhancement in defect growth rate. A number of factors exist which influence the rate at which defects, such as pits/cracks, develop. Included in these are; physical and chemical material surface condition, the nature ofmore » the loading mode, test frequency and electrochemical micro-climate at the metal/solution interface. Based upon corrosion experiments conducted under cyclic and static stress, using low and high strength steels and stainless steels in chloride environments, the following events; surface film breakdown, pit development and growth, pit/crack transition and environment-assisted stage 1 and stage 2 crack growth have been observed. Included in these experiments is that of the Scanning Reference Electrode a technique adapted to evaluate stress-assisted localized corrosion, a process considered to be of primary importance during the early stages of stress corrosion and corrosion fatigue cracking; particularly for actively corroding systems.« less
  • Nitrogen additions of 0.45 to 0.5 wt % to an austenitic stainless steel containing about 22 Cr, 20 Ni and 6 Mo (all wt %) dramatically enhance its resistance to localized corrosion. The electrochemical behavior of this alloy has been studied as a function of chloride ion concentration and temperature. Also, its corrosion resistance has been compared with that of a similar commercial alloy with normal residual nitrogen of only 0.04 wt %. Compositional analyses of the passivated surface of the high nitrogen alloy show an enrichment nitrogen at the metal-passive film interface, with a binding energy similar to thatmore » of the bulk nitrogen on the fully sputtered surface. The role of nitrogen in enhancing the corrosion resistance is discussed in light of the above results and some recent concepts on passivity.« less