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Ben Bouffard
Aluminum coatings were applied to 2024-T3 and 7075-T6 aluminum alloys via the Cold Spray process as an alternative to the conventional toxic chromate conversion coatings currently used in the defense industry. The coatings were applied to substrates with various surface preparation and Cold Spray carrier gas combinations. Some samples were coated with an additional sealant with and without a chromate conversion layer. An exhaustive corrosion analysis was then performed which utilized a number of long term and accelerated tests in order to characterize the corrosion protection of the coatings. RR Moore rotating bend fatigue testing was also performed on commercially pure (CP-Al) coatings applied to AA2024-T351 substrates to study the effect of surface preparation on the coated sample‘s fatigue life. It was found that the pure aluminum coatings offered corrosion protection to the bare AA2024 substrate, and that sealed AA2024 specimens without a chromate conversion layer provided similar protection to those with a chromate conversion layer. Along with providing superior corrosion protection, it was also found that the factor combination of glass bead grit blast surface preparation with nitrogen carrier gas provided the best fatigue life of all samples tested in the rotating bend experiment. These samples experienced an increased average fatigue life, in comparison with bare AA2024 substrates, of 4,751,000 cycles at a stress level of 30 ksi; an increase of 511%. Applying a Cold Spray coating increased the fatigue life of the surface prepared specimen by 20% at a stress level of 26 ksi and 16% at a 30 ksi stress level. Aluminum coatings were applied to 2024-T3 and 7075-T6 aluminum alloys via the Cold Spray process as an alternative to the conventional toxic chromate conversion coatings currently used in the defense industry. The coatings were applied to substrates with various surface preparation and Cold Spray carrier gas combinations. Some samples were coated with an additional sealant with and without a chromate conversion layer. An exhaustive corrosion analysis was then performed which utilized a number of long term and accelerated tests in order to characterize the corrosion protection of the coatings. RR Moore rotating bend fatigue testing was also performed on commercially pure (CP-Al) coatings applied to AA2024-T351 substrates to study the effect of surface preparation on the coated sample‘s fatigue life. It was found that the pure aluminum coatings offered corrosion protection to the bare AA2024 substrate, and that sealed AA2024 specimens without a chromate conversion layer provided similar protection to those with a chromate conversion layer. Along with providing superior corrosion protection, it was also found that the factor combination of glass bead grit blast surface preparation with nitrogen carrier gas provided the best fatigue life of all samples tested in the rotating bend experiment. These samples experienced an increased average fatigue life, in comparison with bare AA2024 substrates, of 4,751,000 cycles at a stress level of 30 ksi; an increase of 511%. Applying a Cold Spray coating increased the fatigue life of the surface prepared specimen by 20% at a stress level of 26 ksi and 16% at a 30 ksi stress level.