![[ Visit Client Website ]](images/banner.gif)
The galvanic ceramic-Al couples were those consisting of Al coupled to titanium diboride (TiB2) and boron carbide (B4C) ceramics which have resistivities of 10-5 and 101 ohm-cm, respectively. The non-galvanic couples consisted of Al coupled to silicon carbide (SiC), silicon nitride (Si3N4), and aluminum nitride (AlN) ceramics which have resistivities of 107, 1014, and 1015 ohm-cm, respectively.
Ceramics and 6061-T6 Al coupons were coupled together using 6061-T6Al
C-clamps. Outdoor experiments were conducted at eight different test sites, to determine the corrosion behavior of the couples in diverse micro-climates and environments (rain forest, alpine, marine, volcanic, industrial, agricultural, and arid) for durations of approximately 3, 6, and 12 months. Statistical analysis was conducted to study the relationship between the atmospheric weather parameters such as humidity, temperature, rainfall, time of wetness (TOW), and chloride deposition rate. The correlation between corrosion rates and atmospheric weather parameters were also studied using statistical analysis. The ingress of environmental constituents across the ceramic-aluminum interface was analyzed using scanning electron microscope (SEM), energy dispersive-X-ray analysis (EDXA), Raman analysis and ion chromatography techniques.
The results from the outdoor exposure tests from different environments showed that the corrosion rates were higher for the galvanic couples as compared to the non-galvanic couples. The statistical analysis showed a strong positive relationship between the weather parameters TOW, humidity and rainfall. Chlorides had an influence on galvanic and crevice corrosion rates of the couples. The two most important parameters that were correlated to the corrosion rates were TOW and the chloride-deposition rate, and the correlation was much stronger for the galvanic ceramic-aluminum couples as compared to the non-galvanic ceramic-aluminum couples.