Synthesis and evaluation of a novel fluorinated poly(hexafluoroisopropyl methacrylate) polymer coating for corrosion protection on aluminum alloy

The hydrophobic and corrosion resistive film of cross-linked poly(hexafluoroisopropyl methacrylate) was successfully prepared by a simple photopolymerization method. The starting materials were a monomer of 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, a photoinitiator of hydroxycyclohexyl phenyl ketone, and a cross-linker of poly (ethyleneglycol diacrylate). A very simple coating technique of drop-casting was used to deposit the fluorinated polymer onto an aluminum alloy substrate (AA 3003). The polymer coating was stable over a 60day period when exposed to an aqueous solution of 3.5% NaCl as measured by open circuit potential technique. The fluorinated polymer coating had high corrosion protection when measured by potentiodynamic polarization with a reduction of 90% in the corrosion current density for the polymer-coated aluminum alloy over the bare substrate. The corrosion current density decreased to 0.065 mu A/cm(2) for the aluminum alloy coated with the polymer film compared to 0.708 mu A/cm(2) for uncoated aluminum alloy. Fourier-transform infrared spectroscopy was used to monitor the polymerization process. The dynamic contact angle technique was used to measure the hydrophobicity for the fluorinated polymer coating and increased from 65 degrees to 100 degrees for the uncoated and coated substrate, respectively. Contact angle measurements before and after treatment with strong acid were carried out to confirm the chemical resistance of the polymer coating. The thermal stability of the fluorinated polymer was measured using thermogravimetric analysis showing thermal stability up to 200 degrees C.