Reactive metal sulfides introduce safety and reliability risks to hydroprocessing (and other) refinery units during outages. Self-heating or pyrophoric catalysts are a concern, as is stress corrosion cracking of sensitized stainless-steel equipment open to air. A nitrite-based aqueous treatment has been developed and deployed in the field, which addresses both catalyst pyrophoricity and polythionic acid (PTA) SCC of equipment. This paper will present case studies where refineries have relied solely upon the nitrite-based oxidizing solution for PTASCC mitigation. Prior published laboratory testing of the nitrite-based oxidizing treatment used spray-applied iron sulfide (FeS) powder and moist air to produce a PTA environment. One limitation of that approach was that the porous nature of the surface does not adequately simulate a “real” FeS layer formed during years of exposure to high temperature sulfidizing processes. This paper presents additional test results on actively loaded bend specimens of ex-service 347H heater tube extracted from an operating diesel hydrotreater unit.