Airplanes-Materials, Aluminum-Testing, Acid rain, Materials-Deterioration, Sulfuric acid, Nitric acid, Seawater, Aluminum-Corrosion
This project examined the damage experienced by 6XXX aircraft aluminum when exposed to simulated acid rain and sea water. An unused heat exchanger cooling fin was cut into samples that were exposed to different combinations of nitric acid, sulfuric acid, and saline. The samples were exposed to six different solution combination for three different time periods. There were six solutions, consisting of a solution of just sulfuric acid, one of just nitric acid, one with sulfuric acid and nitric acid, and then three solutions which were the same as the previous solutions but with the addition of salt water. The three time periods used were 4 days, 1 week and 2 weeks. The scanning electron microscope located at Smith College was then used to assess damage to each sample. The results from the scanning electron microscope showed that all solutions caused damage, shown as pitting on the surface of the aluminum. The samples which were placed in the sulfuric acid and salt water solution were damaged more heavily, instead of the surface pitting, visible aluminum flakes were being removed from the sample. This was attributed to a reaction within the solution between the sulfuric acid and the sodium chloride which could have created hydrochloric acid and sodium sulfate. The addition of the hydrochloric acid could be the source of the heavier damage. Reasoning behind the reduced damage on the sulfuric acid, nitric acid and salt water sample is that the sodium nitrate might have caused corrosion retardation, shown by almost no damage change at between the first and second time step. All other samples saw surface pitting where the depressions grew larger over time. The combination of sulfuric acid and salt water caused the most severe damage, and the solution with nitric acid and salt water caused the least amount of damage. It was concluded that acid rain can cause damage to aircraft grade aluminum, and damage will be more severe in locations near salt water.
Beall, Taylor Marie, "Analysis of environmental damage to aircraft aluminum" (2013). Honors Project, Smith College, Northampton, MA.
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