CORROSION BEHAVIOR OF STAINLESS STEELS IN SULFURIC ACID CONTAINING Fe**3** plus AND Cl** minus .

The effects of Cl** minus and Fe**3** plus on the dissolution of stainless steels in 5-25% H//2SO//4 were studied at 75 degree C. The dissolution of types 304 and 321 is retarded by 100-5000 ppm Cl** minus . The dissolution of type 316, on the other hand, increases with the Cl** minus concentration in the range of 100-1500 ppm and decreases on further additions of Cl** minus up to 5000 ppm. These effects of Cl** minus can be explained by the change of cathodic polarization behavior. The simultaneous presence of Cl** minus and Fe**3** plus above certain concentrations causes pitting, general dissolution and the combination of both, depending on the concentrations. The latter form of corrosion is the result of the change in the corrosion potential from the pitting region to the active region, caused by the change of the anodic polarization curve as pits develop.