Francine S. Bovard

Technical Note: Corrosion Potential for Aluminum Alloys Measured by ASTM G 69

Abstract ASTM G 69, “Standard Practice for Measurement of Corrosion Potentials of Aluminum Alloys,” is a useful method to discern the temper of a given aluminum alloy. Corrosion potentials (Ecorr) often can be used to differentiate between different alloys since copper or zinc in solid solution will cause significant differences in Ecorr. Measured Ecorr of various aluminum alloys and other non-aluminum metals were listed.

Corrosion Performance of New Generation Aluminum-Lithium Alloys for Aerospace Applications

Over the past several years, a new generation of aluminum-lithium alloys has been developed. These alloys are characterized by excellent strength, low density, and high modulus of elasticity and are therefore of interest for lightweight structural materials applications particularly for construction of current and future aircraft. These new alloys have also demonstrated significant improvements in corrosion resistance when compared with the legacy and incumbent alloys. This paper documents the superior corrosion resistance of the current commercial tempers of these materials and also discusses the corrosion performance as a function of the degree of artificial aging. Results from laboratory corrosion tests are compared with results from exposures in a seacoast atmosphere to assess the predictive capability of the laboratory tests. The correlations that have been developed between the laboratory tests and the seacoast exposures provide confidence that a set of available methods can provide an accurate assessment of the corrosion performance of this new generation of alloys.

Development of an Improved Cosmetic Corrosion Test for Finished Aluminum Autobody Panels

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion. This paper summarizes the analyses of the results from the laboratory tests and the OEM test track exposures.