The Failure That Had Nothing to Do With the Alloy Grade A heat exchanger in a refinery developed through-wall pitting within 18 months of commissioning. The tubes were specified correctly, the mill certificate confirmed the right alloy, and the installation inspection showed nothing unusual. The plant team replaced the bundle and assumed it was a manufacturing defect. It wasn't. The metallurgical testing on the failed tubes told a different story entirely. EDS analysis of the