2011 EFFICIENCY OF INHIBITORS OF CHLORIDE-INDUCED CREVICE CORROSION OF A Ni-Cr-Mo ALLOY Mauricio Rincón Ortíz, Martín A. Rodríguez and Ricardo M. Carranza Depto. Materiales - Comisión Nacional de Energía Atómica Instituto Sabato - Univ. Nac. de San Martín / CNEA Av. Gral. Paz 1499 San Martín, B1650KNA Buenos Aires, Argentina mrincon@cnea.gov.ar Raul B. Rebak GE Global Research 1 Research Circle, CEB2505 Schenectady, NY 12309, USA ABSTRACT Alloy 22 was considered as a candidate for the engineered barrier of the USA repository and it is still considered among the candidates in the scoping work for the argentine repository system. Chloride ion is the only species present in groundwater that is able to promote crevice corrosion, if severe conditions such as high temperatures and a tight crevice are present. Other species present in groundwater have shown to be inhibitors or non-detrimental species. The objective of this work was to evaluate the efficiency of different species potentially found in groundwaters as possible inhibitors of crevice corrosion of alloy 22. A modification of the THE method (ASTM G 192) was used for determining the crevice corrosion repassivation potential of alloy 22 in chloride plus inhibitor solutions at 90ºC. The species tested as inhibitors were nitrate, sulfate, carbonate, bicarbonate, chromate and molybdate anions. The critical ratio for the complete inhibition ranged from 0.2 to 2. Nitrate was the most efficient among tested in- hibitors. The carbonate was the only species of the carbonate / bicarbonate / carbonic acid equilibrium able to inhibit the chloride-induced crevice corrosion of alloy 22. Sulfate, chromate and molybdate were moderately goods inhibitors. Keywords: N06022, chloride, crevice corrosion, repassivation potential, inhibitors INTRODUCTION Alloy 22 (N06022) 1 is a well known member of the Ni-Cr-Mo family of alloys. It was de- signed to withstand the most aggressive industrial applications in both reducing and oxidizing acids 2,3 . It contains nominally 22% chromium (Cr), 13% molybdenum (Mo) and 3% tungsten ©2011 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 1440 South Creek Drive, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. 1 Paper No. 11204