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Overview of Naphthenic Acid Corrosion (NAC)

Naphthenic Acid Corrosion (NAC) is an acidic environment "disease" well known in the refining industry. Unlike many acid corrosion problems, NAC is associated with dry hydrocarbon streams (no water phase). There are a variety of organic acids associated with naphthenic acids in different crudes, and each can have a different impact on the actual corrosion rates experienced. NAC is typified by dozens of small localized "pock marks" and grooving type corrosion surrounded by full thickness material, however some lower alloys can corrode by general thinning. Typically, the higher the temperature of the hydrocarbon stream (up to 800F or 427C), the more severe the NAC will be, up until the streams move into cat crackers and hydroprocess units where the organic acids are destroyed. 


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