Corrosion Behavior of High-Strength Steel for Flexible Riser Exposed to CO_2-Saturated Saline Solution and CO_2-Saturated Vapor Environments

The corrosion behavior of high-strength steel used for flexible riser exposed to CO_(2-)saturated saline solution and CO_(2-) saturated vapor environments was studied through immersion experiment and electrochemical corrosion experiment. The corrosion behavior and mechanism of the tested steel were analyzed on the basis of corrosion kinetics, nature of corrosion products, corrosion product morphology, elemental distribution and polarization curves. The experimental results showed that the microstructure of the tested steel was bainitic microstructure. The corrosive activity of the tested steel exposed to CO_(2-) saturated vapor environment was significantly lower than that exposed to CO_(2-) saturated saline solution environment.On prolonging the exposure time, the corrosion rate gradually decreased, the corrosion heterogeneity increased, and the dimensions of FeCO_3 crystals gradually became small. At later stages of corrosion, the corrosion current density decreased significantly and the anodic Tafel slope increased, indicating that the corrosion process was strongly inhibited. The corrosion mechanism of low-alloy steel with bainitic microstructure was proposed based on experimental results.

Effect of heat treatment on corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3Mo carbon steel

Before and after heat treatment,0Cr15Ni5Cu3MoN stainless steel(SS)samples were immersed in sulfate-reducing bacteria(SRB)environment to study the effect of heat treatment on the antimicrobial properties of Cu-containing stainless steel.The effect of heat treatment on the corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3MoN SS was studied by scanning electron microscopy,transmission electron microscopy,laser scanning confocal microscopy,and electrochemistry.The results show that 0Cr15Cu3 SS has better antibacterial properties with fewer bacteria adsorbed on the surface after heat treatment,and its corrosion resistance is significantly improved.Interestingly,on the 7th day of immersion,the corrosion resistance of the heat-treated stainless steel was lower than that of the rolled stainless steel.This was due to the fact that the rolled samples were protected by biofilm at this time,while the surface bacteria on the heat-treated samples died,resulting in the exposure of the substrate surface and thus reducing the corrosion resistance of the heat-treated samples.Thus,because of the strong bactericidal properties of the heat-treated Cu-containing stainless steel,the corrosion resistance of the samples suddenly decreases in the middle stage of corrosion,and this discovery provides a new view to study the corrosion process of Cu-containing stainless steel in the SRB environment.