STRESS-CORROSION CRACKING BEHAVIOR OF STAINLESS-STEELS WITH RESPECT TO THEIR USE IN ARCHITECTURE .1. CORROSION IN THE ACTIVE STATE

Unexpected failures on 18/8 CrNi and 17/12/2 CrNiMo steels in indoor s wimming pool atmospheres made it necessary to reinvestigate chloride i nduced stress corrosion cracking (SCC). SCC in the active state was in vestigated 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 temperatu res up to 50-degrees-C. Selected tests were performed on the material with the highest SCC susceptibility, 1.4301, in solutions with differe nt concentrations of hydrochloric acid and sodium chloride. SCC was on ly 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 high ly 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 1 0% nickel (1.4301, 1.4303, 1.457 1) exhibited very pronounced SCC. The other materials with nickel cont ents distinctively higher or lower proved, respectively, to be less su sceptible or resistant to SCC. Thus, the same effect of nickel content was observed as is known for resistance to chloride induced SCC in th e passive state. All materials were prone to pronounced general corros ion. The corrosion phenomena observed were completely different from t he swimming pool failures reported.