Failure Analysis of Tuna Cans

A metal container used for food packaging must preserve the food’s edibility characteristics for a long period of time. Lacquered tinplate is suitable for canning food provided that the cans are airtight. This article details a root cause failure analysis that was conducted utilizing a sample of tuna cans taken from an affected batch of one million units. Several examinations were carried out to identify the failure’s root cause: visual examination, SEM fractography, micro-hardness measurement, and microstructural characterization. The cracks are located in the HAZ of the welded zone. As a result of the examinations carried out, the authors were able to identify the cause of the primary failure. The identified fracture mechanism is that of stress corrosion cracking (SCC), due to both the aggressive environment (high water content in the oil) and the low lacquer adhesion caused by superficial welding irregularities.