The effect of Cl- ions on corrosion evolution of NiCu low alloy steel during immersion tests （up to 70 days） in deaerated 0.05 mol/L bicarbonate solutions was investigated by in-situ electrochemical mea- surements c...The effect of Cl- ions on corrosion evolution of NiCu low alloy steel during immersion tests （up to 70 days） in deaerated 0.05 mol/L bicarbonate solutions was investigated by in-situ electrochemical mea- surements combined with X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA） characterisations. The results showed that due to the acceleration of substrate dis- solution in the presence of Cl, corrosion of NiCu low alloy steel underwent only two stages, i.e., a quick oxidation process followed by a final metastable passive state, without the initial slow anodic dissolu- tion as observed in the Cl--free bicarbonate solution. The main components of the formed rust layer in the Cl--free bicarbonate solution were α-FeOOH and Fe3O4, while apart from α-FeOOH, Fe6（OH）12CO3 was found evident instead of Fe3O4 in the Cl-containing solution. Metastable pits were only found in the Cl-containing solution where Cl- accumulated after the immersion test, confirming the attack of Cl on the substrate after penetrating the formed corrosion product layer.展开更多
文摘The effect of Cl- ions on corrosion evolution of NiCu low alloy steel during immersion tests （up to 70 days） in deaerated 0.05 mol/L bicarbonate solutions was investigated by in-situ electrochemical mea- surements combined with X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA） characterisations. The results showed that due to the acceleration of substrate dis- solution in the presence of Cl, corrosion of NiCu low alloy steel underwent only two stages, i.e., a quick oxidation process followed by a final metastable passive state, without the initial slow anodic dissolu- tion as observed in the Cl--free bicarbonate solution. The main components of the formed rust layer in the Cl--free bicarbonate solution were α-FeOOH and Fe3O4, while apart from α-FeOOH, Fe6（OH）12CO3 was found evident instead of Fe3O4 in the Cl-containing solution. Metastable pits were only found in the Cl-containing solution where Cl- accumulated after the immersion test, confirming the attack of Cl on the substrate after penetrating the formed corrosion product layer.
