Philip T. Wille
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The standard equipment used for accelerated corrosion exposure testing is the ASTM B117 chamber. Exposure conditions consist of a 3.5% NaCl salt solution that is sprayed into the chamber with one or more atomizing nozzles. The exposure zone of the chamber is maintained at a temperature of 35'2 'C (95'3'F). Exposure time depends on specific experiments and/or material being tested. The problem with this method, however, is that it does not always accurately simulate typical conditions out in the field. Outdoor conditions contain various amounts of UV and ozone which are not present in a standard B117 exposure chamber test. The objective of this experiment is to compare how differing amounts of UV and ozone in a B117 chamber will affect the rate of corrosion of various metals. Ultimately, the goal is to achieve a reliable correlation between the rate of corrosion in the field and the modified B117 chamber. The performance of five different metals (6061Al, 2024Al, 7075Al, Cu, and 1010 steel) was evaluated. Two different levels of UV and ozone were used for each of four experiments: high UV/high ozone, low UV/low ozone, high UV/low ozone, and low UV/ high ozone. High and low UV had a radiative flux of 0.96W/m2 and 0.1 W/m2, respectively; ozone was adjusted from 800ppb to 100ppb for high and low, respectively. Mass loss data was taken for each metal at every 100 hour mark, up to 1000 hours. At high UV and high ozone levels, corrosion rate increased for all exposed metals. At low UV and high ozone levels the corrosion rate decreased for each metal except for steel, where the corrosion rate remained relatively equal. Since steel does not form a passive oxide layer, this suggests that UV may be disrupting the passive oxide layers of the copper and aluminum alloys.
Douglas C. Hansen
Primary Advisor's Department
Materials Degradation and Electrochemical Engineering (Research Institute-Materials Engineering)
Stander Symposium poster
"Rates of Corrosion of Various Metals in a Modified B117 Chamber and Their Correlation to Field Data" (2013). Stander Symposium Posters. 371.