Service exposure has been accrued in 66 steam generators tubed with Inconel-600. Localized corrosion coincident with sludge deposition in low flow-velocity zones has been observed. Inter granular cracking has been attributed to stress-assisted caustic corrosion resulting from hydrolysis of condenser inleakage contaminants or sodium phosphate reactions with feedwater corrosion products. Wall thinning or wastage is attributed to the formation of high-concentration sodium phosphate solutions under the sludge blanket. The resistance of Inconel-600 to these corrosion mechanisms is comparable or superior to that of other candidate tube materials. The experience gathered points strongly to environmental and thermal/hydraulic factors rather than materials considerations as the predominant influence on the occurrence of localized corrosion. Mechanical modifications designed to reduce the number of tubes in zones of low flow-velocity are being installed into operating units; current production units have incorporated design features including a flow distribution baffle to improve the thermal/ hydraulic conditions over prior models. Rigorous control of feedwater impurities is being applied to reduce the probability of creating a corrosive environment in the steam generators.