Correlation Studies between Outdoor Exposure and Accelerated Laboratory Corrosion Tests for Galvanic and Non-Galvanic Ceramic-Aluminum Couples

摘要

Correlation of outdoor exposure corrosion-rate data from a variety of microclimates (i.e., rain forest, alpine, marine, volcanic, industrial, agricultural, and arid) with a series of accelerated laboratory corrosion tests (controlled humidity-chamber and cyclic corrosion test chamber experiments) for both galvanic and non-galvanic ceramic-aluminum (Al) couples were studied. Due to galvanic effects by relatively conductive titanium diboride (TiB_2) and boron carbide (B4C) ceramics, high corrosion rates were observed in 6061-T6 Al coupons coupled to these ceramics. Corrosion rates of the 6061-T6 Al coupons in the non-galvanic couples with silicon carbide (SiC), aluminum nitride (AlN), or silicon nitride (Si_3N_4) were lower. Accelerated laboratory corrosion tests conducted with chloride-Containing solutions were aggressive and did not always represent the outdoor exposure results. Hence, the outdoor exposure test data were used to adjust the duration and treatment of the accelerated corrosion tests so that the corrosion damage accumulated in the accelerated tests could better represent the corrosion damage accumulated in the field. Accelerated laboratory corrosion experiments conducted with less aggressive sodium sulfate solution treatments more accurately simulated the outdoor corrosion trends.