Corrosion performance of carbon steel in CO 2 aqueous environment containing silty sand with different sizes was investigated by immersion tests and electrochemical measurements. Silty sand could form an adsorption layer on steel surface in initial period, and the sand adsorption layer was turned into a mixture film of silty sand with corrosion product in last period. The adsorption layer in 325 mesh condition (large size) had the fewest pores for H 2 CO 3 transport, exhibiting the highest cathodic current inhibition. In spite of little corrosion product, the sand adsorption film formed in 325 mesh condition induced the lowest corrosion rate. For 1000 and 5000 mesh silty sand, the sand adsorption layer had some pores for H 2 CO 3 transport, leading to low cathodic current inhibition and much matrix dissolution. But the adsorption layer for 5000 mesh silty sand (small size) had the largest special surface area to accelerate heterogeneous precipitation of corrosion product FeCO 3 . Therefore, the mixture film in 5000 mesh condition was more compact, exhibiting stronger anodic inhibition and lower corrosion rate than those in 1000 mesh condition.