The effect of Cr, Ni and Mo on the corrosion behaviours of highly alloyed materials was investigated in simulated sour well environments. The increases of all of Cr, Ni and Mo contents increase the resistance to general and pitting corrosion. Increasing Ni content also improves the resistance to stress corrosion cracking (SCC). From the standpoint of those resistances, high Ni content as well as high Cr and Mo contents is essential to maintain the corrosion resistance in sour well environments. Surface film analysis shows there are two types of film structures, that is, Cr oxide single layer, and double layer with outer Ni sulfide and inner Cr oxide. The corrosion resistance is basically determined by the presence of surface Cr oxide film. Increasing Ni and Mo contents are considered to increase the stability of the surface film. In addition, electrochemical measurements were carried out with high alloy materials and pure metals to clarify the behaviours of Cr, Ni and Mo.

Subject
Double layer, Materials, Corrosion resistant alloys, Metal surfaces, Nickel based alloys, Molybdenum alloys, Sour environments, Sulfide films, Structures, Oxide films, Oxide surfaces, Pitting, Corrosion resistance
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1984
Association for Materials Protection and Performance (AMPP)
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