Abstract: The scanning Kelvin probe (SKP) technique, in combination with energy dispersive spectrum (EDS) analysis of corrosion products, was employed to investigate the initial corrosion behavior and potential distribution of Q235 carbon steel and Q450 weathering steel during salt spray test. The results showed that Q235 carbon steel was severely attacked by Cl^-. During the initial period of salt spray test, anodic and cathodic areas formed on the surface of the specimens and the surface potential became more and more positive in the corrosion procedure with a distinct character of localized corrosion. The SKP results showed that Q450 weathering steel was inclined to uniform corrosion, whose surface potential was more positive than that of Q235 carbon steel, probably being due to the effect of alloying elements. The product layer of Q450 was more compact, which indicated that Q450 was more resistive to atmospheric corrosion than Q235.