Science-Based Corrosion Resistant Design for Aerospace and Defense

At more than $20 Billion annually, corrosion is a major cost of maintaining defense equipment and facilities [1]. But more than that, corrosion, and in particular galvanic corrosion between dissimilar materials, is a primary cause of structural failure that puts aircraft and other equipment out of service. The present approach for considering galvanic incompatibilities is simplistic. It is simplistic in that the only thing it takes into account is the galvanic potential difference between two adjacent materials. An estimate of the galvanic corrosion severity is usually based on some form of galvanic potential table, as in MIL-STD-889 and ASTM G82. However, in mixed material assemblies it is found that the electrochemical kinetics of the materials determines the severity of corrosion in addition to the galvanic potential difference (ΔE), and the two are not directly related. A better way of predicting galvanic corrosion using mixed potential approach is proposed. Although this approach has been around for decades, up to this point in time there has never been enough robust and consistent data to use it. This paper presents a simple software tool that employs this methodology designed to aid galvanic corrosion assessment by the use of a curated electrochemical database and help to bring this approach more mainstream. Alternatively, discussion on numerical technique based corrosion models to deal with more complex problems, that have become increasingly relevant for simulation, lifetime prediction, and optimization of corrosion prevention measures. This paper will in general present the approach, challenges and limitations of present galvanic corrosion assessment methods. Followed by the introduction of a proposed ‘new’ method, its advantages, requirements, and the efforts associated to adoption of this new method at DoD level. In addition, some examples on the issues involved with common galvanic interfaces in service today, and demonstrate the use of this new computational tools to assess galvanic corrosion severity and proposing better solutions to minimize corrosion.