Failure Analysis and Fitness-for-Service Assessment of Nickel 200 Baffles in PVC Reactor

Visual inspection of Nickel 200 (Ni-200) baffles inside several Type 304L reactor vessels used to produce PVC revealed corrosion in the form of localized metal loss along the baffle’s length direction. Prior to recent process changes, these baffles had operated satisfactorily for about 8 years. The observation of metal loss raised concerns as to the cause of the corrosion, and the possibility of compromised structural integrity of the reactor baffles. A failure analysis was performed to characterize the nature and extent of the corrosion, based on scrape samples and cut-out samples. A Level 3 fitness-for-service assessment per API 579 was performed to evaluate the urgency for repairs. Laboratory corrosion testing was then done to further investigate the influence of pH, oxygen, and temperature, on the corrosion susceptibility of the Ni-200 material in this application.