QUARTERLY REPORT OF THE SOLUTION CORROSION GROUP FOR THE PERIOD ENDING APRIL 30, 1958

Abstract

6 9 2 4 8 < E 5 0 2 5 H 5 of a solution containing 0.04 M UO/sub 2/SO/sub 4/, 0.025 M D/sub 2/SO/sub 4/, 0.03 M CuSO/sub 4/ and 750 ppm of nickel as nickel sulfate at 300 deg C in D/sub 2/0 but both nickel and copper were lost from solution when the nickel concentration was increased to 1700 ppm. The chemical stability of a solution containing 0.036 M UO/sub 2/SO/sub 4/, 0.022 M D/sub 2/SO/sub 4/, 0.009 M CuSO/sub 0.013 M NiSO/sub 4/ and 0.0016 M MnSO/sub 4/ in D/sub 2/0 was also demonstrated at 300 deg C. The corrosion of stainless steel in 0.04 M UO/sub 2/S/sub 4/O/sub 4/ containing 0.025 M H/sub 2/SO/sub 4/ and 0.0 1 M CuSO/sub 4/ was found to be relatively severe above the critical velocity at 250 and 300 deg C. The critical velocities observed were 10 to 20 and 30 to 40 fps, respectively at 250 and 300 deg C. Loop runs in which oxygen was removed from solution have shown that as uranium precipitated excess acid, ferrous and nickelous ions formed. On addition of oxygen to such a solution, uranium dissolved and ferrous ions were oxidized to ferric ions which precipitated from solution. A sixth test of the bellows and stainless steel-Zircaloy-2 traasition joint mockup was completed satisfactorily. The total exposure of the mockup was 9153 hr, including 8600 hr on fuel solution 312 thermal cycles between 300 and 1OO deg C and 518 mechanicai deflections. Tests to determine if type 304 stainless steel York mesh would corrode appreciably in uranyl sulfate solutions containing iodine and a hydrogen and oxygen atmosphere at 1OO deg C produced negative results. No significant corrosion of the steel was observed. A solution of 0.04 M U0/sub 2/S0/sub 4/ containing 0.04 M BeSO/sub 4/ and O.0O5 M CuSO/sub 4/ proved to be unstable during a 200-hr run at 280 deg C. Both uranium and beryllium were lost from solution. The addition of 100 ppm ruthenium as rthenium nitroso sulfate to a 0.02 M UO/sub 2/SO/sub 4/ solution containing 0.025M H/sub 2/SO/sub 4/ and 0.01 M CuSO/sub 4/ at 250 deg C provided substantial inhibition of corrosion of stainless steel. However, the inhibition appeared to be due to the substantial quantities of chromium(VI) that formed in the presence of ruthenium. A solution of 0.17 M U0/sub 2/S0/sub 4/ containing 0.20 M Li/sub 2/SO/sub 4/, 0.10 M H/sub 2/ S0/sub 4/, and 0.02 M CuSO/sub 4/ was stabl e at 280 to 295 deg C and was only slightly more corrosive to stainless steel at 250 deg C than 0.17 M U0/sub 2/S0/ sub 4/ without additives. Tests of inhibitors of corrosion of stainiess steel in 0.05 M H/sub 2/SO/sub 4/ at 250 deg C showed 0.002 M potassium dichromate to be very effective. 0.04 M MgSO/sub 4/ and 0.05 M Li/sub 2/SO/sub 4/ also gave substantial inhibition though not so much as expected. 0.02 M U0/sub 2/S0/sub 4/ had little effect. Stress-corrosion cracking characteristics of a number of alloys were investigated under conditions in which steam-heated pipe bends of the materials were cooled by a spray of chloride-containing potable water. MST Gr 3 titanium and Croloy 16-1 stainless steel did not crack during 5000-hr of exposure. Inconel and Nionel were resistant to cracking during test periods of 1000 and 2000 hr, respectively. Incoloy T cracked in 1000 hr. Cold-formed type 347 stainless steel pipe bends did not crack provided the surface was shot-blasted or cathodically protected with aluminum. Normally, coldformed bends of the alloy crack during 1000 hr. Annealing; of type 347 stainless steel pipes did not completely eliminnte susceptibility to cracking but did reduce the frequency of cracks. No cracking of the alloy was experienced during a 1000-hr run in which the cooling water was added slowly enough to allow flash vaporization. Stress specimens of several alloys were tested in distilled water at 300 deg C containing oxygen and 100 ppm of chloride. Generally, at pH 10.5 the high nickel alloys such as Nionel and Incoloy were more resistant to cracking than the austenitic stainiess steels. However,