An extension of Wagner's analysis of competing scale formation

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00738292· OSTI ID:6074478

Wang, Ge; Gleeson, B; Douglass, D L ^[1]

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1. Univ. of California, Los Angeles (United States)

When an alloy reacts with a gas, such as oxygen or sulfur, the characteristics of the scale which forms are dependent on a number of factors. In particular, the concentration of the alloying constituents and their affinity for the gas greatly affect what the phase constitution of the resulting scale will be. Wagner's criterion to predict the minimum concentration of solute (N{sub B(min)}{sup 0}) necessary for the exclusive formation of its scale has been modified to incorporate both thermodynamic and kinetics requirements. The analysis presented here involves a receding alloy/scale interface for which the composition of the alloy at this interface is governed by thermodynamic equilibrium between the two competing scale phases and the base alloy. This is a more rigorous analysis than that of Wagner's, who assumed the alloy/scale interface to be immobile and the solute composition at the interface to be zero. A comparison is made between values of N{sub B(min)}{sup 0} found experimentally and those predicted by Wagner's and the present criterion for a number of alloy-gas systems. It is shown that the criterion developed in the present analysis can often provide a better approximation of the actual N{sub B(min)}{sup 0}. The expressions derived from the present analysis have been extended also in a semiquantitative manner to provide a criterion for the minimum amount of solute in the alloy required for the transition from internal to external scale formation.

• OSTI ID: 6074478
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 35:3-4; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOY SYSTEMS
ALLOYS
BINARY ALLOY SYSTEMS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CORROSION PRODUCTS
DATA
DIFFUSION
EQUATIONS
INFORMATION
INTERFACES
KINETIC EQUATIONS
KINETICS
MATHEMATICAL MODELS
OXIDATION
PHASE STUDIES
REACTION KINETICS
SCALING
SULFIDATION
THERMODYNAMIC ACTIVITY
THERMODYNAMICS