Abstract Slow strain rate tests (SSRT) were conducted in solutions of hydrochloric acid (HCl) + sodium chloride (NaCl) at ambient temperature on type 304 (UNS S30400) stainless steel (SS) weldments that exhibited a duplex ferrite-austenite structure in the weld fusion zone. Results indicated the weld fusion zone corroded preferentially. Stress corrosion cracking (SCC) initiated and propagated along the ferrite-austenite interphase. Austenitic dendrite was observed by scanning electron microscopy (SEM) in the fracture surface morphology. This interfacial cracking was attributed to the formation of a complex cell structure consisting of weld fusion zone/parent metal with delta-ferrite/austenite in the weld zone. The delta-ferrite was microanodic phase. The proposed model of SCC for type 304 SS weldments in HCl + NaCl was film formation-slip (film rupture)-dissolution-crack propagation. Because of the presence of the complex cell structure, the surface film was nonuniform, which was favorable for crack initi...