Effect of intensity of ultra-violet light on inhibition of stress corrosion cracking for sensitized SUS304 stainless steel

The effect of irradiation of ultra-violet(UV) light on stress corrosion cra cking(SCC) behavior for sensitized SUS304 stainless steel in a deaerated 10 (-3) kmol.m(-3) NaCl solution at 368 K has been investigated by using a slo w strain rate testing(SSRT) apparatus with a dynamic observation system. Th e UV light, whose range of wavelength was from 250 to 400 nm, was emitted b y a mercury lamp, and was irradiated to the specimen through the test solut ion. In order to change an intensity of the UV light, some neutral density filters were set in front of the quartz glass window on the cell. A potenti al of -200 mV(Ag/AgCL) was applied to the specimen before and during SSRT, and the UV light was irradiated up to the strain showing almost the yield s tress. It was obvious that the SCC initiation was inhibited by the UV light irradiation to the specimen during SSRT. Crack initiation frequency varied with the light intensity, and an optimum intensity range existed for inhib iting crack initiation completely. On the other hand, the crack propagation rate showed almost no dependence on the irradiation conditions. In the cas e that the UV light was irradiated to the shielding material mounted in fro nt of the specimen, a lot of cracks were initiated on the specimen, similar to the case without irradiation. This fact indicates that the SCC is not i nfluenced by the solution chemistry altered by the UV light irradiation.