Properties of thermally sprayed fluoropolymer PVDF, ECTFE, PFA and FEP coatings

Thermally sprayed fluoropolymer, polyvinylidene fluoride (PVDF), ethylene chlorotrifluoroethylene (ECTFE), perfluoroalkoxy alkane (PFA) and fluorinated perfluoroethylenepropylene (FEP) coatings were produced by flame and plasma spraying processes. It was possible to produce high quality coatings by these techniques. These coating processes are one-step methods in which post heat treatments are not required, in contrast to conventional electrostatic deposition methods. Morphology and particle size distributions were determined for each fluoropolymer powder. The coatings prepared by plasma and flame spraying were studied by optical microscope, salt spray test and liquid immersion tests. Sprayed coatings were found to be poreless and very smooth. In salt spray test, no corrosion invasion was found. In both liquid immersion tests (pH values -0.7 and 14) only PFA coating performed well. The other coatings showed a little corrosion in liquid immersion tests. That was observed as darkening of the fluoropolymer coating in the areas that were exposed to corrosive liquid. According to sectioned micrographs, the coatings were fully dense.