Material tests in deaerated 20 % NaOH and 20 % NaOH+5% NaCl solutions at 325 degC. Final report

In SVF Project 30: 'Comparative corrosion tests of different tube materials for PWR steam generators' the materials AISI 321, alloy 800, alloy 600, Inconel 690 and Nickel 201 have been autoclave tested in deaerated 20% NaOH and 20% NaOH+5% NaCl solutions at 325 deg C as to stress corrosion cracking resistance. In all 374 single and double U-bends from 15 different heats in at least one and up to as many as five different material conditions have been exposed up to 2000 h in both environments (2500 h regarding shot-peened U-bends from four heats). Nickel 201 was found to be entirely resistant to stress corrosion cracking in both environments. All the remaining materials showed on the contrary cracking to a varying degree. Thus alloy 800 showed better resistance to stress corrosion cracking than alloy 600 in both environments and was found to be the most resistant alloy next to Nickel 201. Shot--peening was found to be very effective in checking stress corrosion cracking in these environments, without causing any appreciable deterioration of the general corrosion resistance of the materials. (author)