High-temperature electrochemical tests have resulted in the stress corrosion cracking of Inconel-600 and Incoloy-800 (registered trademarks, International Nickel Company), and Type 304 stainless steel in caustic solutions. Results show that stress corrosion cracking of these alloys can be prevented or accelerated by varying their electrochemical potential. To a certain extent, the same effect can be achieved by altering the gas atmosphere above the test solution from a pure nitrogen cover gas to a mixture of 5% H2 and 95% N2. The effect of the cover gas can then be negated by adjusting the specimen’s electrochemical potential either to cause or to inhibit stress corrosion cracking. These types of experiments lead to a better determination of the boundary conditions within which stress corrosion cracking of the alloys occurs. Some specifics of the test results reveal that in deoxygenated caustic solutions, Inconel-600 cracks intergranularly at mildly anodic potentials; Incoloy-800 cracks transgranularly at reduced potentials (at or near the open circuit potential) and intergranularly at highly oxidizing potentials; and cracking is mixed (transgranular/intergranu-lar) for Type 304 stainless steel at or near the open circuit potential. The severity of cracking for both Inconel-600 and Incoloy-800 in deoxygenated caustic solutions is reduced by giving the materials a simulated post-weld heat treatment (1150°F for 18 h). Test results on Inconel-600 show that high-carbon (0.06%) material cracks less severely than low-carbon (0.02%) material, in both the simulated post-weld heat-treated condition and the mill-annealed condition. The results we obtained with the electrochemical corrosion techniques agree with results obtained using conventional corrosion methods for caustic stress corrosion cracking. Moreover, many metallurgical variables, which promote or retard caustic cracking, are the same as those conditions that promote or retard high-temperature high-purity water failures—particularly in the case of Inconel-600.