On the extension of CP models to address cathodic protection under a delaminated coating
Cathodic protection models for pipeline and other metallic structures developed to address the presence of coating flaws or holidays do not account explicitly for the presence of a delaminated region surrounding a holiday. The potential drop in the delaminated region was obtained by solving the coupled, non-linear, partial differential, governing equations that describe transport and electrochemical reactions within the delaminated region. The results were used to develop an analytic expression for the potential drop across the delaminated region as a function of delaminated region length and the resistivity of the bulk environment exterior to the holiday. Expressions developed using this approach can be utilized by existing cathodic protection models to deliver improved potential distributions along protected metallic surfaces. The simulations were used to test the commonly employed assumption that transport by diffusion can be neglected in the delaminated region. The influence of diffusion on current was shown to be significant.
A Mathematical Model for Cathodic Delamination of Coated Metal Including a Kinetic pH–Porosity Relationship
A mathematical model for the delamination of coating from active metal was developed in the presence of multiple electrochemical reactions, homogeneous reactions, and precipitation of corrosion product. The computational results illustrate that the propagation of potential front is controlled by the production of OH - ions along the metal-coating interface, while that of porosity front is limited by the rate constant of bond-breakage reactions. The movement of the two fronts are close when the time constant associated with breaking bonds is small as compared to that of diffusion and migration processes. When the time constants of bond-breakage and coating degradation are large, the velocity difference between the potential and porosity fronts becomes large. The delamination rate and delamination mechanism predicted from the model are in good agreement with experimental interpretations. A systematic sensitivity analysis for the fitting parameters used in the program was conducted and the results show that the computations are most sensitive to the parameters in the porosity-pH relation.
The Meaning of Wisdom in James: Examination of a Hypothesis
The following essay is an attempt to examine the manner in which the writer of the Epistle of James uses the concept of Wisdom; and to study the suggestion that the way in which he uses it is more or less interchangeable with that in which other writers of the New Testament use the concept of the Holy Spirit.