Effects of silty sand on localized corrosion behavior of 3Cr steel in CO_2-O_2 aqueous environment

摘要

Corrosion behavior of 3Cr steel in CO_2-O_2 aqueous environment containing silty sand with different sizes was investigated by immersion tests and electrochemical measurements. The results showed that corrosion rate and corrosion morphology of 3Cr steel were affected by the size of silty sand. Silty sand could form an adsorbed layer on steel surface. The adsorbed layer in 5000 mesh condition had more pores for O_2 transportation and O_2 could promote cathodic reaction. Cr(OH)_3 deposited on steel surface and 5000 mesh silty sand could not separate the Cr-rich corrosion product. Therefore, a Cr-rich corrosion film formed on 3Cr steel surface, resulting in uniform corrosion and low corrosion rate. However, in 1000 mesh condition, the sand adsorbed layer with less pores blocked O_2 transportation to steel surface. The cathodic current decreased, but the integrity of the Cr-rich corrosion film was destroyed by 1000 mesh silty sand. Consequently, the tendency of local matrix dissolution increased, therefore 3Cr steel exhibited localized corrosion and high corrosion rate in 1000 mesh condition.