ABSTRACT

Modern technologies combine materials of different nature next to each other within the same structures. This new concept leads however to an increased risk of galvanic corrosion which needs to be thoroughly analyzed. The present work aims thus to apply novel techniques to the study of a typical case such as the Fe-Al galvanic couple. Localized Electrochemical Impedance Spectroscopy (LEIS) results are compared to the developed computational model for validation and to predict the worst-case scenario leading to galvanic corrosion. The electric-potential model provides highly valuable information not derivable from AC analysis. Nevertheless, the AC LEIS model currently under development will allow for a better interpretation of the unconventional LEIS features observed.

INTRODUCTION

Modern technologies combine materials of very different nature within the same structures. Such selection seems to be primarily dictated by a balance between cost and performance. In the automotive and aerospace industries, the requirement to reduce fuel consumption and CO2 emissions led to the so- called ”light” and ”green” designs.1 The concept of ”light car” is based on the combination of high strength steels with lighter materials having comparable mechanical properties, e.g., aluminum and magnesium alloys.1 A similar selection of materials is being introduced in new aircraft designs. However, questions arise regarding the galvanic compatibility of such arrangements especially when different materials are located on neighboring structure parts.

Aluminum or magnesium alloys may form galvanic couples with steel, leading to severe and unpredictable corrosion of the most active material. Moreover, a combination of different alloy forms (e.g. cast and wrought) or alloy grades, introduces stringent requirements on the necessary surface treatment processes essential for corrosion prevention. Thus, galvanic corrosion can become the ultimate limiting factor in deciding the applicability of such material combinations. In this direction, the corrosive behavior of the prospect material couples needs to be thoroughly studied.2 Moreover, upgraded methodologies for corrosion prevention need to be developed.

This content is only available via PDF.
You can access this article if you purchase or spend a download.