A high damage rate was found on the inner surface of a Phosphoric Acid Evaporator Chamber. A substitution of the original poly-isoprene or natural rubber (NR) liner was proposed. Lack of wet erosion comparative data, demanded to perform laboratory erosion- corrosion tests on possible substitutes: fluorinated ethylene-propylene copolymer (FEP); polyvinylidene fluoride (PVDF); ethylene-tetrafluorethylene copolymer (ETFE); and superalloy UNS N08700 (wt. %: 24Ni, 20Cr, 4.5Mo; 1.5Cu, Fe bal.) Non-standardized tests were performed using a stirring system with four flat samples as blades, which rotated in a mixture of H3PO4, with 20 wt. % SiC grits. The temperature was kept at 70°C. The rotating speed was held at 1800 r.p.m. The duration of the test was 1100 hours. Dry erosion tests were also carried out to compare results. They were done according to ASTM C 704 specification. The abrasive particles used were SiC grits. The incidence angles were 30 ° and 45 °. The test was set up according to the ASTM C 704 specification. The weight and volume loss was measured for all samples (wet and dry tests), and the surface morphology of the damaged areas was observed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and laser profilometry technique. Results showed that, although there were differences, all material tested could be used, so an economic analysis was made. This showed that all fluoropolymers tested, when used as liner in a dualaminate vessel (fluoropolymer liner in a fiberglass reinforced plastic, FRP, structure) were considerably more economical.
Key words: Corrosion - erosion, phosphoric acid, dry erosion, wet erosion, FEP, ETFE, PVDF, NR, superalloy UNS N08700, dualaminated constructions, FRP, cost