Abstract: A novel polymer alloy coating is provided consisting essentially of polyphenylene sulfide and an amount of polyimide. The polyimide is produced by the crosslinking and curing of an acetylene terminated aromatic polyimide oligomer resin. The amount of polyimide utilized is sufficient to enhance the adhesiveness of the polyphenylene sulfide to a metal substrate without substantially changing the melt flow properties, chemical resistance and thermal stability of the polyphenylene sulfide. A polymer alloy resin composition is also provided for application to the metal substrate to produce the polymer alloy coating. The novel polymer alloy coating is particularly suitable for coating pipes, particularly pipe couplings for oil and gas well production pipes which are exposed to extreme temperatures, pressures and corrosive environments.