Corrosion of Metallic Materials in High Temperature and Concentrated Sulphuric Acid

Summary

The problem of the corrosion resistance of metallic materials to sulphuric acid solutions at various concentrations and temperatures is related to the various nature of the cathodic process developed by the acid. Hydrogen evolution is the process mainly promoting corrosion at the lowest acid concentration, while S-containing ions can promote cathodic processes at more noble potentials. Electrochemical and corrosion rate measurements indicated that among the commercial alloys, silicon-iron materials are the most resistant materials to the hot concentrated sulphuric acid solutions; active-passive alloys such as Fe, Cr, Ni and Mo alloys can behave satisfactorily only in determinated acid concentration depending on the potentials at which the cathodic process occurs. At the higher acid concentrations molybdenum as alloying element, plays a beneficial effect.

Polarization resistence method for monitoring the corrosion rates can give useful and correct informations for the determination of the instantaneous corrosion rates.