Numerical Simulation of Micro-Galvanic Corrosion of Al Alloys: Effect of Chemical Factors

Abstract

© The Author(s) 2017. Published by ECS. All rights reserved. A finite element model for simulating the propagation of micro-galvanic corrosion of Al alloys induced by intermetallic particle was established to reveal the dynamic changes including a moving dissolution boundary, deposition of reaction products and their blocking effect. This model has previously been used to study the influence of geometrical factors such as the particle size and width of the anodic ring. In this work, we explore effects of chemical factors including pH and bulk concentration of O 2 by using chemical-dependent electrochemical kinetics as input parameters. The simulations reveal that the micro-galvanic corrosion rate is slowest at pH = 6. For pH > 6, the rise of pH increases the dissolution rate of Al and also the deposition rate of Al(OH)3, leading to a faster but more short localized Al dissolution. For pH < 6, the decline of pH accelerates Al dissolution and inhibits Al(OH)3 deposition, leading to a faster and more long lasting Al dissolution. At pH ≤ 4, deposition of Al(OH) 3 becomes negligible, and localized corrosion will propagate continuously. Within the O 2 concentration range relevant for atmospheric conditions, a lower O 2 concentration in the solution leads to a slower rate of micro-galvanic corrosion.