Corrosion rate (mm/year) was examd. in six grades of (17.2-21.9%)Cr-(9.4-25.1%)Ni steel in the intermediate absorption tower, hydraulic seat (gas temp., 208 degrees C; acid concn., 97.9%; acid temp., 95.5 degrees C), beneath acid distributor (72.5 degrees C, 97.8%, 82.4 degrees C), under mist eliminators (72.5 degrees C. 97.8%, 82.4 degrees C), and in the final absorption tower, hydraulic seal (180.7 degrees C, 98.6%, 83.9 degrees C), beneath acid distributor (73.4 degrees C, 98.0%, 83.9 degrees C), and under mist eliminators (74.7 degrees C, 98.0%, 81.2 degrees C). At higher temps. and higher acid concns. the 18.5-21 % steel was the most resistant.. At lower temps. and acid concns., the 18.7-9.4% was equiv. to the 18.5-21 % (< 0.1 mm/year). In aerosols, each grade was equally resistant (< 0.1 mm/year).