Abstract
Exposure of semi-crystalline poly(phenylene sulphide) (PPS) coatings to a simulated geothermal environment containing acid (pH ~ 1.6) brine at 200°C resulted in a decline in its crystallinity over time. This decrease was due primarily to an increase in the degree of hydrothermal oxidation of the PPS surfaces, thereby lowering their resistance to wear from blasting. To improve the resistance of the coating’s surfaces, aluminium oxide-rich calcium aluminate (ACA) fillers were incorporated into the PPS. The sulphuric acid in the brine permeated through the coating, and then preferentially reacted with calcium in the ACA to form water-soluble calcium sulphate which leaches out from ACA particles during exposure. The hydrothermal hydration reactions of calcium-depleted ACA led to the formation of a well-crystallized boehmite coexisting with the PPS. The in-situ growth of boehmite crystals formed in the ~ 65 μm-thick surface layer reinforced the oxidation-damaged PPS, and improved the coating’s resistance to blasting wear. Also, PPS coatings containing an appropriate amount of ACA showed a better performance in protecting the underlying steels against corrosion than that of the bulk PPS coatings without ACA.