科研之友
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摘要
Laboratory salt spray testing has been used for many years to accelerate natural atmospheric exposures with limited success. The corrosion of silver represents a stark example of the failings of such testing. In virtually any field environment, silver corrodes measurably in a month, but after 4 months in a standard salt spray test, no corrosion of silver is observed. The present work is concerned with the modification of the conventional salt spray corrosion test and its correlation to field measurements of silver. Two subsystems were designed and constructed to modify a conventional salt spray chamber. One subsystem consisted of ultraviolet A (UVA) lamps mounted on a movable rack, which allows them to be positioned to achieve the desired UVA light intensity. The other subsystem consisted of an ozone system based on a commercial ozone generator and a distribution manifold that allowed a uniform concentration of ozone to be maintained throughout the chamber. As constructed, the system can produce 50 W/m2 of UVA light and ozone concentrations up to 23.2 ppm. The system was then used to modify the protocol of ASTM B117. The results from the modified B117 test are correlated with the corrosion behavior and performance observed in field exposures. The corrosion products formed during the modified B117 exposure are the same as those observed after field exposures. Silver chloride (AgCl) was the main dominant corrosion product. Non-uniform corrosion occurred, and metallic silver grains were observed on the surface. The large acceleration factors obtained demonstrate that both ozone and UVA light can be used to replicate the type of corrosion found on silver at a wide range of geolocations. The extent of the acceleration can be controlled by the ozone concentration and the intensity of the UVA light.
- 出版日期2012-3
- 单位沈阳建筑大学
