CORROSION BEHAVIOR OF HIGHLY ALLOYED STAINLESS-STEELS IN MIXED CHLORIDE AND FLUORIDE AQUEOUS-SOLUTIONS

Laboratory weight loss and cyclic potentiodynamic polarization corrosi on tests were performed on two types of corrosion resistant alloys, a duplex alloy (ferritic-austenitic stainless steel) and two austenitic stainless steels, in mixtures of chloride (3000, 9000 and 15000 ppm) a nd fluoride (4800 and 15000 ppm) ions at pH 3. Two temperatures were t ested, 60 and 70 degrees C. The electrochemical results indicate that the duplex stainless steel presents high corrosion resistance. Weight loss results show low corrosion rates of the two types of stainless st eels after 60 days exposure. Some pits-crevices were found under the c orrosion crust deposits on the duplex stainless steel.