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• High Fe 3 C content accelerated the formation of a passive film on the Cr steel surface in silty sand containing solution. • Increasing Cr content in steel enhanced the contents of Cr 2 O 3 and Cr(OH) 3 in the passive film. • Silty sand increased carrier densities of the passive films and reduced the protective effects of the films. • Corrosion mechanism of the Cr steel with silty sand based on the combined effect of Fe 3 C and Cr contents was illustrated. The effect of Cr content in steel on its passivation behavior in a CO 2 aqueous environment containing silty sand was investigated. The results indicated that the stability of passive film was improved with increasing Cr content. High Fe 3 C content accelerated the rapid formation of a passive film as well as precipitates and dislocations. Increasing Cr content enhanced the contents of Cr 2 O 3 and Cr(OH) 3 in the passive film. Silty sand increased carrier densities of passive films, thereby reducing their protective effects. The role of the contents of Fe 3 C and Cr on corrosion mechanism of Cr steel with silty sand was emphasized. [ABSTRACT FROM AUTHOR]

The effect of silty sand on the dynamic mechanism of corrosion products formed on carbon steel in a CO 2 environment containing 3.5 wt% NaCl and 0.1 wt% NaHCO 3 is investigated. Silty sand has a dual effect on the corrosion products structure. First, silty sand presents on the surface, and embeds in the Fe 3 C network. Then, silty sand delays the FeCO 3 precipitation, and changes the FeCO 3 crystals growth manner and structure. Silty sand decreases active surface area, but this effect is less significant than FeCO 3 precipitation. Consequently, silty sand first alleviates, then promotes general corrosion rate, while always alleviates localized corrosion. • Silty sand first reduces, then raises C R g e n e r a l , while always mitigates localized corrosion. • Silty sand has a dual effect on the structure of corrosion products. • Silty sand presents on the surface, and embeds in the porous Fe 3 C network. • Silty sand delays FeCO 3 precipitation and changes its growth manner and structure. • Silty sand reduces S act , but this effect is less significant than FeCO 3 precipitation. [ABSTRACT FROM AUTHOR]

The interaction of silty sand and corrosion products layer in sweet environment was evaluated. Corrosion protection was a function of two factors, i.e., adsorption and embedment of silty sand, and the presence of corrosion products layer. Silty sand could block ions transportation and slow down the dissolution of FeCO 3. The main protection was offered by corrosion products, this effect was more significant in the presence of a full coverage FeCO 3 layer. FeCO 3 -rich layer not only prevented the embedment of silty sand but also reduced the adsorption. Silty sand and corrosion products layer exhibited an obvious antagonism effect. • Corrosion reduction relied on silty sand and corrosion products. • The main corrosion protection was offered by corrosion products. • FeCO 3 -rich layer prevented the embedding of silty sand and reduced the adsorption. • Silty sand slowed down the dissolution of FeCO 3 crystals. • Silty sand and corrosion products layer exhibited an obvious antagonism effect. [ABSTRACT FROM AUTHOR]