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Corrosion behavior of 300M in neutralcorrosion environments containing Na Clsimulated by totalimmersion(TI),salt spraying(SS)and periodic immersion(PI),was investigated by surface analysis techniques,corrosion weight-loss method,and electrochemicalmeasurements.In totalimmersion environment,rust on the steelconsisted of a porous outer rust layer with main constituent of γ-Fe OOH,and an inner rust layer of dense Fe_3O_4 film with network broad cracks.In salt spraying environment,outer rust with main composition of γ-Fe OOH/α-Fe OOH/Fe_3O_4 was compact,and inner rust showed dense Fe_3O_4 film.Rust formed by periodic immersion exhibited a compact outer rust layer with constituent of α-Fe OOH/γ-Fe OOH/Fe_3O_4 and an inner rust layer with composition of α-Fe OOH/α-Fe_2O_3;inner rust showed a ultra-dense film adherent to the steel.The corrosion rate showed a rule of vss(salt spraying)>vti(totalimmersion)>>vpi(periodic immersion)in 0-240 h,and vss≈vti?vpiin 240-720 h.The rust formed by periodic immersion was dense and compact,with stable electrochemicalproperties,and had excellent protection on the steel.Humidity and oxygen concentration in allthe environments played major roles in rust formation.
Corrosion behavior of 300M in neutral corrosion environments containing Na Clsimulated by totalimmersion (TI), salt spraying (SS) and periodic immersion (PI), was investigated by surface analysis techniques, corrosion weight-loss method, and electrochemical measurements. the steelconsisted of a porous outer rust layer with a main constituent of γ-Fe OOH, and an inner rust layer of dense Fe_3O_4 film with network broad cracks.In salt spraying environment, outer rust with main composition of γ-Fe OOH / α-Fe OOH / Fe_3O_4 was compact, and inner rust showed Dense Fe_3O_4 film. Rust formed by periodic immersion exhibited a compact outer rust layer with constituent of α-Fe OOH / γ-Fe OOH / Fe_3O_4 and an inner rust layer with composition of α-Fe OOH / α-Fe 2 O 3; inner rust showed a ultra-dense film adherent to the steel. Corrosion rate showed a rule of vss (salt spraying)> vti (total immersion) >> vpi (periodic immersion) in 0-240 h, and vss ≈ vti ≈ vpiin 240-720 h.The rust formed b y periodic immersion was dense and compact, with stable electrochemical properties, and had excellent protection on the steel. Humidity and oxygen concentration in all the environments played major roles in rust formation.