| Abstract: | Unexpected failures on 18/8 CrNi and 17/12/2 CrNiMo steels in indoor swimming pool atmospheres made it necessary to reinvestigate chloride induced stress corrosion cracking (SCC). SCC in the active state was investigated on stainless steels 1.3974, 1.4301, 1.4303, 1.4439, 1.4462, 1.4522, 1.4539 and 1.4571 by testing under constant load at temperatures up to 50°C. Selected tests were performed on the material with the highest SCC susceptibility, 1.4301, in solutions with different concentrations of hydrochloric acid and sodium chloride. SCC was only observed in critical ranges of hydrogen-ion concentration and only in conjunction with pronounced general corrosion. In a solution with c(HCl) = 1.0 mol/l and c(NaCl) = 0.5 mol/l, which had proved to be highly SCC-inducing, the effects of different parameters on SCC behaviour were studied. Temperature, stress level and degree of cold deformation exerted only a secondary influence, in contrast to alloy composition: austenitic steels containing about 10% nickel (1.4301, 1.4303, 1.4571) exhibited very pronounced SCC. The other materials with nickel contents distinctively higher or lower proved, respectively, to be less susceptible or resistant to SCC. Thus, the same effect of nickel content was observed as is known for resistance to chloride induced SCC in the passive state. All materials were prone to pronounced general corrosion. The corrosion phenomena observed were completely different from the swimming pool failures reported. |
