Computational design and optimization of multilayered and functionally graded corrosion coatings

• Published in: Corrosion science 2013-12, Vol.77, p.297-307
• Main Authors: Cross, Samuel R., Woollam, Richard, Shademan, Stephen, Schuh, Christopher A.
• Format: Article
• Language: English
• Subjects: Applied sciences; B. Modeling studies; C. Cathodic protection; Coatings; Computation; Corrosion; Corrosion environments; Corrosion prevention; Design engineering; Exact sciences and technology; Mathematical models; Metals. Metallurgy; Optimization; Protective coatings
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2013.08.018

•We present a computational approach optimize functionally graded coatings for cathodic protection.•Galvanic protection of steel by zinc alloy coatings can be improved by more than 100% by introducing a composition gradient.•An optimized coating structure consists of a thin barrier layer, grading to a thick sacrificial layer.•Computational optimization can produce non-obvious coating designs with large improvements in coating performance. This paper describes a computational approach to analysis and optimization of compositionally graded coatings for cathodic protection. Time-dependent galvanic corrosion is simulated by coupling a finite element electrochemical model with calculated rates of metal dissolution. A simulated annealing optimization algorithm is applied to the time-dependent corrosion model to determine coating structures that maximize desired protective qualities. This computational approach to coating design is applied to a hypothetical graded zinc-alloy coating with a circular defect on an iron substrate, in an aerated NaCl electrolyte. A linear compositional gradient increases the predicted duration of cathodic protection by 84% over an equivalent monolithic coating, while the optimized coating structure further improves protection time to a total increase of 112%. The optimized coating structure consists of a thin barrier layer adjacent to the substrate, with a thicker sacrificial layer on the exterior and a short region of graded composition in between. The overall approach to optimization of coating structure is shown to be robust, efficient, and produce non-obvious designs with significant improvement in coating performance, and thus has potential to be of significant utility in practical corrosion coating design.