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Combined influence of fluorides and ferric ions on corrosion of titanium and Pd alloyed titanium in 100 g L−1 sulfuric acid solution

Abstract In hydrometallurgical applications, titanium and its alloys are used as construction material in the most aggressive environments. Under acidic conditions, fluorides are known to be deleterious to titanium, but it is not well known how the presence of small amounts of both fluorides and ferric ions influences the corrosion behaviour of titanium in sulfuric acid solutions. Unalloyed titanium grade 2 (Ti Gr. 2) and palladium alloyed grades, titanium grade 17 (Ti Gr. 17) and titanium grade 7 (Ti Gr. 7), were investigated with electrochemical techniques and immersion tests in 100 g L−1 sulfuric acid, containing 30 mg L−1 fluorides and two levels of ferric ions, 0·3 and 3 g L−1. It was found that the addition of fluorides accelerated the uniform corrosion rate, especially for the unalloyed Ti Gr. 2 in the solution having the lower amount of ferric ions. Palladium alloying was found to have a beneficial effect in reducing the uniform corrosion rate in the presence of small amounts of fluorides.