Date of Graduation

Spring 2018

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Applied Mathematics - BS/MS

Research Sponsor

Dr. Curtis Clemons

First Reader

Dr. Gerald Young

Second Reader

Dr. Kevin Kreider

Abstract

This research focuses on coupled galvanic/pitting corrosion of AA7075 when combined with stainless steel in a fastener assembly. A one-dimensional mathematical model of a well-mixed thin film electrolyte is developed to predict the damage profile of the AA7075 surface when its protective coating is damaged. The damage exposes the galvanic couple. A time dependent system of partial differential equations for potential, chloride concentration, aluminum ion concentration, and damage is developed and solved numerically. Two approaches to calculate the current density within aluminum pits are discussed. The first is a current balance between the cathodic, anodic and passive portions of the metal surfaces. This reflects the local chemistry that drives pit growth early on before any growth of oxide to repassivate the metal. The second approach is based on the work of McKinnon [1], using the potential calculated at the bottom of each initiated pit with a polarization curve relevant to the pit chemistry. This approach reflects the growth of pits during the formation of oxide, and leads to the repassivation of pits. Now that the model and solution scheme have been formulated, the next step is to carry out the simulation, and compare results to experimental results.

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