ELECTROCHEMICAL METHOD FOR TESTING OF THE CORROSION BEHAVIOR OF AUSTENITIC CRNIMO-STAINLESS STEEL WELDMENTS

Austenitic CrNiMo stainless steel welds can be more susceptible to pitting and crevice corrosion than the base material owing to segregation and precipitation in the heat affected zone, in the high temperature zone and in the welded zone. Suitable test methods are needed to optimize welding technology. Comparison of potential curves (DIN 50 919), comparison of critical pitting corrosion temperatures in FeCl3- or other model solutions, visual estimation after longterm corrosion tests with or without electrochemical load are discussed. A small measurement cell heated from the rear with circulating and temperature controlled electrolyte is shown. With its help separate areas of a weld can be electrochemically investigated. Welds of the materials X 2 CrNiMoN 17 12 2 (1.4406), X 2 CrNiMoN 17 13 5 (1.4439) and X 1 NiCrMoCu 31 27 4 (1.4563) are tested in acidic NaCl solutions in the range of 25 to 75-degrees-C. Critical pitting corrosion potentials are obtained for base materials, heat affected zone and weld material. An influence of the welding energy is probable, but cannot be proved in this case without statistical certainty.