Corrosion Resistance of Silane Coatings on Aluminum and Magnesium Alloys

John Demopoulos


The purpose of this project was to increase the corrosion resistance of aluminum and magnesium alloys by coating the coupons with a silane on the surface. Four different silanes: 3-aminopropyltriethoxysilane (APTES), Bis(triethoxysilylpropyl)amine (Bis), (Heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane (FTS), and (Heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (non Cl FTS) will be used and compared to see which silane would give the best corrosion resistance. Each silane solution was coated on the coupons by using a solution method in which the coupon was submerged for 24 hours and then thermally cured for another 24 hours. Once the coating was applied, the water contact angle and the thickness of the coating were measured. Then the metal coupons were subject to a corrosion test by immersing them in sodium chloride and oxalic acid solutions for 7 days. The weight loss of the metal coupon was measured after the immersion test. All the silane coatings provided an increased corrosion resistance for aluminum alloy AA2024-T3, and the only silane, APTES, tested on magnesium alloy AZ 31 also significantly reduced its corrosion in both corrosive solutions. The FTS coating provided the best corrosion resistance on the aluminum alloys in an oxalic acid solution and the Bis solution had the best corrosion resistance in the sodium chloride solution. With the addition of a silane coating, aluminum and magnesium alloys used in industry will have an increased corrosion resistance and will increase the life of the part so it will not need to be replaced.