Corrosion behaviour of steel in concentrated phosphoric acid solutions

The corrosion rates of steel in concentrated phosphoric acid (1.0-11.0 M) were determined by the weight loss method, at three temperatures 298, 308 and 323 K. Results obtained show that corrosion rate increases with both acid concentration and temperature. The logarithm of corrosion rate was fitted against the acid concentration, values of Hammett Ho and Strehlow Ro(H) functions. The activation energies, enthalpies and entropies of the dissolution process were determined.