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The localized corrosion induced by (Ca, Mn)S-(Al, Mg)O complex inclusions was investigated. It revealed that MgO·Al 2 O 3 served as cores and MnS·CaS as shells in the carbon steel. MnS and CaS acted as an anodic phase in the galvanic corrosion formed with steel matrix, while MgO and Al 2 O 3 had no galvanic couple effect with MnS and CaS. MnS was the most preferentially dissolved and triggered localized corrosion, which expanded in the order of CaS-Fe-MgO·Al 2 O 3. The driving force for sulfides and steel matrix dissolution was the effect of galvanic couple, and high local plastic deformation caused by oxides, respectively. • MnS and CaS could form the galvanic corrosion with steel matrix, while MgO and Al 2 O 3 had no galvanic couple effect. • MnS was the most preferentially dissolved as an anodic phase and triggered localized corrosion. • Pit nucleated at the MnS position, and expanded in the order of CaS-Fe-MgO·Al 2 O 3. • Driving force for carbon steel matrix dissolution was the effect of high local plastic deformation caused by MgO·Al 2 O 3. [ABSTRACT FROM AUTHOR]

The effect of reversed austenite on the pitting behavior of super 13Cr martensitic stainless steel (S13Cr MSS) was investigated. The results revealed that reversed austenite was a FCC structure with Ni enrichment after tempering process, and there were no Ni-depleted regions adjacent to it. The reversed austenite content increased with increasing tempering temperature, and the pit depth decreased, as well as the dispersion degree of the Kelvin potential distribution. The reversed austenite reduced the risk of pitting corrosion through increasing the passive film compactness, and inhibiting Cl- penetration. Accordingly, the pitting corrosion resistance was enhanced as the tempering temperature increased. • Ni enriched reversed austenite content increased as the tempering temperature increased. • Reversed austenite formation restricted the movement of dislocations and reduced the dislocations density in the S13Cr MSS. • Reversed austenite reduced pitting corrosion through increasing the passive film compactness and inhibiting Cl- penetration. • High reversed austenite content led to the good pitting corrosion resistance for S13Cr MSS. [ABSTRACT FROM AUTHOR]

• The Volta potential of Cr-depleted regions was lower than that of steel matrix and the regions were dissolved preferentially. • Increasing Cr contents in the Cr-depleted regions hampered the effect of Cr deficiency in the weak passive film. • Low width and density of Cr-depleted regions reduced the intensity of pits on steel surface. • High Cr contents and low Cr-depleted regions width and density led to good pitting corrosion resistance for 0Cr13 MSS. The effect of M 23 C 6 precipitates on the pitting behavior of 0Cr13 martensitic stainless steel (MSS) was investigated. The results revealed that the precipitates in the 0Cr13 MSS with different tempering temperatures were all M 23 C 6 with a face-centered cubic (FCC) structure. The Cr-depleted regions had approximately 6 mV Volta potential lower than the steel matrix. The increasing Cr contents in the Cr-depleted regions hampered the effect of Cr deficiency in the weak passive film. The low width and density of Cr-depleted regions reduced the intensity of pits on steel surface. The pitting corrosion resistance was enhanced as the tempering temperature increased. [ABSTRACT FROM AUTHOR]

• 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 effect of Cr content on the corrosion behavior of Ni-Mo steel in the tropical marine atmospheric environment is systematically investigated. The increase of Cr content accelerates the aggregation and the enrichment of Ni element, and thus promotes the formation of an inner electronegative film which attracts positively charged ions including Mo6+, Mo4+, Ni2+ and Cr3+ ions, and repels negatively charged Cl- ions. Cr promotes the formation of more nano-FeOOH and the conversion of γ-FeOOH into α-FeOOH. A small amount of chromium promotes the formation of micro-pits at the initial stage, and with time, those micro-pits gradually accumulate into pieces. • Adding a small amount of Cr into Ni-Mo steel reduces the corrosion rate. • An electronegative inner film composed of Cr and Ni elements attracts Mo6+, Mo4+, Ni2+ and Cr3+ ions, and repels Cl- ions. • Cr 2 O 3 acts as the nucleation site of FeOOH, generating more nano FeOOH, and doping Cr promotes the transformation of γ-FeOOH to α-FeOOH. [ABSTRACT FROM AUTHOR]

The effect of Cl- concentration on the corrosion behavior of Cr-containing steel in tropical marine atmospheric environment is systematically studied. Cl- ions affect the adsorption amount of water film and then affected O 2 diffusion. They reduce the generation of NiFeO 4 and Cr(OH) 3 and destroy the electronegativity of inner film, further weakening the homologous enrichment of Ni, Mo and Cr and intensifying the penetration of Cl- ions. The amount of NiO and Cr 2 O 3 decreases due to oxygen reduction, which reducrs FeOOH nucleation sites and promotes the large-size FeOOH generation, leading to increase the pores in the corrosion product films. • Adding a small amount of Cr to Ni-steel reduces its corrosion rate. • Cr element promote more NiFe 2 O 4 forming and attract more Ni2+ and Cr3+ ions, repelling and shielding negatively charged Cl-. • High Cl- concentration reduces the content of O 2 , inhibiting the formation of NiFe 2 O 4 and Cr(OH) 3. [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]

The effect of tensile elastic stress on passivation behavior and surface chemistry of 2205 duplex stainless steel is investigated. Elastic stress increases the potential drop at the film/solution interface, donor density and defects diffusion coefficient, resulting in the increase of passive current density. High elastic stress (≥60%σ s) leads to the generation of soluble CrO 3 , the increase of oxidized Cr and Fe(Ⅱ) content and the decrease of film thickness, resulting in the quasi-steady-state current density no longer independent of potential. Passive film become denser from spontaneous passivation to primary passivation and Fe(III) compounds dominate the passive film under secondary passivation. • Passivation of 2205 DSS under elastic stress is studied. • Elastic stress results in the increase of I ss by decreasing d and increasing φ f / s , N D , and D 0. • High elastic stress (≥60% σ s) leads to further increase of I ss , which is no longer independent of potential. • Elastic stress facilitates the increase of oxidized Cr and Fe(Ⅱ) content. • Potential makes passive film become denser until transpassivation occurs. [ABSTRACT FROM AUTHOR]

The corrosion behavior of weathering steel in the environments with different NaCl concentrations was systematically investigated. The results indicated a decrease of corrosion resistance of steel as NaCl concentration increased. While, the weight gain rate in high concentration was lower than that in lower conditions, which was attributed to the inhibition on the diffusion of O 2 caused by the residual NaCl solution. Cu, Ni and Mo can mutually promote the agglomeration process and improve the performance of the rust layer in low NaCl concentrations, which was severely inhibited in high NaCl concentrations, resulting in a loose rust layer. • Corrosion behavior of the weathering steel in different NaCl concentration conditions was studied. • The phase compositions and valence states of Cu, Ni and Mo in the rust layer were characterized. • Based on the principle of the Raoult's law, the formation mechanism of rust layer was proposed. [ABSTRACT FROM AUTHOR]