Admicellar polymerization and characterization of thin poly(2,2,2-trifluoroethyl acrylate) film on aluminum alloys for in-crevice corrosion control.

Corrosion control of aluminum alloys in the aerospace industry has been of great interest in recent years, especially the aging of certain fleets in the United States Air Force. A thin film of poly(2,2,2-trifluoroethyl acrylate) (PTFEA) has been deposited on aluminum alloy coupons by admicellar polymerization for the purpose of in situ control of corrosion in narrow gaps. Polymerization conditions were chosen based on contact angle measurements, and the final product film was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Surface characterization studies have shown that the polymeric film is approximately 10 nm thick with nonuniform deposition at this scale. The modified surface is highly hydrophobic and able to delay salt solution uptake (3.5 wt % NaCl) for a period of up to 6 h in crevice corrosion tests. PTFEA films reduced the corroded area to 20% compared to 65% for a bare aluminum control and to 33% for poly(methyl methacrylate) (PMMA) film in a 24 h crevice test. PTFEA film exhibits better corrosion protection than PMMA film because it has higher hydrophobicity than a PMMA-modified surface and comparable properties as a corrosion barrier.