Through static state simulation test in high pressure Cauldron as well as EPMA and XRD surface analysis

it is obtained that the Cl - has an inhibitory action to the film-formation on carbon steel in high-temperature boiler water under low phosphating water treatment condition

along with the growth of Cl - concentration

the corrosion pits densely appeared

but the pitting attack isn’t obvious when Cl -concentration is lower than 0.2mg/L. For test piece with complete film-formation

the film hadn’t been obviously dissolved and pitting attack not occurred when the Cl - concentration reached 1mg/L. For test piece with film-formation and pitting attack

the original corrosion pits were deepened and enlarged obviously when the Cl - concentration was 0.2mg/L

producing small corrosion pits all around. It is found after composition analysis of typical corrosion pits that the Cl - were enriched around said pits

and the main composition on the surface of film was Fe 3O 4.