科研之友
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摘要
Analysis of a magnesium-rich primer (MgRP) and a full chromate coating system on AA2024-T3 panels exposed at two field sites, Pt. Judith, RI and a University Oceanographic Laboratory Ship (UNOLS) based out of Seattle, WA, for 2 y were compared to identical samples exposed in a B117 test chamber (2,000 h) and a modified salt fog chamber equipped with ultraviolet (UV) radiation and ozone gas (2,000 h). Both coating systems utilized a topcoat of polyurethane. The analysis was performed utilizing Fourier transform infrared (FTIR) attenuated total reflectance on multiple locations for each panel. Comparison of the spectra for the UV/ozone chamber and field exposure samples to the baseline data for one formulation of topcoat in the MgRP coating system indicated that a decrease in the % reflectance peaks for various components of the polyurethane had occurred, suggesting the degradation of the urethane component of the topcoat. The observed change in the FTIR spectra indicating topcoat degradation on the field and modified chamber exposures is in contrast to the spectra from the samples exposed to the ASTM B117 protocol, which looks more like that of the baseline data. The FTIR data for the full chromate coating system formulation tested in the UV/ozone chamber also indicate that exposure condition is more aggressive in causing the degradation of the coating system components than the ASTM B117 test exposure. Together, these results suggest that it is possible to tailor the chamber exposure conditions to yield coating degradation specific to an exposure site in the field where the synergistic effects of UV and ozone are involved in the degradation process.
- 出版日期2016-11
