Polyphenylene-sulphide (PPS) and polyphenyletheretherketone (PEEK) have high heat and corrosion-resistant performance. Thermal sprayed coatings of PPS and PEEK have been produced by the HVAF spray system. The molecular structures of these coatings have been analyzed by Fourier Transform Infrared Spectrophotometer (FT-IR) and Differential Scanning Calorimeter (DSC). The microstructures of cross-section and surfaces of these coatings have been observed. The formation mechanism of these coatings has been estimated as follows; (1) PPS and PEEK powders are melted and oxidized during thermal spraying. However, the amount of coating oxidation is very small, so that high anti-corrosion performance of sprayed coatings is obtained. (2) These coatings have some pores including the incomplete melting particles. However, it is estimated that these pores are closed-pores.