The Effect of Molybdenum on Stainless Steels and Naphthenic Acid Corrosion Resistance

摘要

Molybdenum containing austenitic stainless steels are specified for naphthenic acid corrosion resistance in crude units. There are many unanswered questions as to how and why molybdenum increases resistance to this corrosion mechanism. This paper will try to document the current state of knowledge on the protective mechanism and the history of increasing molybdenum content versus increased TAN (Total Acid Number) values. Material selection of stainless steels with 2% Mo, 2.5% Mo, 3% Mo, and 6% Mo will be discussed along with case histories of successes and failures. Using information collected from laboratory and operating experience we will attempt to define factors affecting resistance versus molybdenum content and draw conclusions as to what level of molybdenum content is needed as a function of TAN.