Effect of Dissolved Oxygen on Pitting Corrosion Behavior of Low-Alloy Steel under Hydrostatic Pressure

Abstract

Effect of dissolved oxygen on pitting corrosion behavior of low-alloy steel under hydrostatic pressure in neutral 3.5 wt.% NaCl solution was investigated by scanning electron microscope (SEM), 3-D measuring microscope and so on. The results show that the combined effect of hydrostatic pressure and dissolved oxygen increases the overall growing rate of corrosion pits and causes deeper corrosion pits but decreases their sizes in the horizontal direction. Electrochemical measurement results reveal that dissolved oxygen dominate the corrosion kinetics of low-alloy steel in the environment containing high hydrostatic pressure and high dissolved oxygen by accelerating cathodic process, slowing down the anodic process and promoting open circuit potential (OCP). Consequently, the increased charge transfer process makes the pits have a larger volume and depth. Meanwhile, the decreased initial potential energy difference based on energy theory calculation at the initiation site by dissolved oxygen possibly inhibits the pitting growth in the horizontal direction.

Coupling Effect of Hydrostatic Pressure and Erosion on Corrosion Behavior of X70 Steel in Simulated Seawater

“…By observing the anodes and cathodes of the polarization curves, it is found that the polarization curve shapes at 2 to 15 MPa are similar to those of the erosion–corrosion experiment, which is a combination of uniform corrosion and pitting (Figure ). The anodic polarization curve with a lower slope has no inflection point at 0.1 MPa; the cathode polarization curve hardly changes in the potential range of −0.64 V to −0.7 V. The diffusion of oxygen is considered the key to controlling the corrosion rate. ,,, In addition, the open circuit potential is much higher than other conditions at 0.1 MPa, indicating that the metal has higher thermodynamic stability and a lower tendency for corrosion . Pressure increases the corrosion rate of the X70 steel not only by affecting the thermodynamic stability of the material but also by promoting corrosion kinetics of the material.…”

“…The corrosion products at the edge of the pit are rich in O and Cl, while Fe is more concentrated in the middle area where pitting and uniform corrosion are connected. Moreover, the energy spectrum identified Si and Mn, which primarily exist in the inclusion phase and are nucleation points that induce pitting corrosion …”

“…Moreover, the energy spectrum identified Si and Mn, which primarily exist in the inclusion phase and are nucleation points that induce pitting corrosion. 29 …”

“… 16 , 26 , 28 , 35 In addition, the open circuit potential is much higher than other conditions at 0.1 MPa, indicating that the metal has higher thermodynamic stability and a lower tendency for corrosion. 29 Pressure increases the corrosion rate of the X70 steel not only by affecting the thermodynamic stability of the material but also by promoting corrosion kinetics of the material. Using molecular dynamics modeling, Liu et al 36 revealed that pressure-promoted anodic dissolution mainly amplifies the Ψ1 effect by decreasing the thickness of the Helmholtz layer on the metal surface.…”

Structure, Surface Morphology, Chemical Composition, and Sensing Properties of SnO2 Thin Films in an Oxidizing Atmosphere

“…Oxygen absorbed on a layer’s surface reduces its conductance, emergence, and rises its work function (in the range of 423–723 K) [ 12 , 13 ]. On the other hand, the control of oxygen concentration is crucial in cooling, food production [ 14 , 15 ], gardening [ 16 ], diagnostics [ 17 ], and alarm devices such as oxygen monitors for the atmosphere or water [ 18 , 19 ], where improper oxygen concentrations lead to underwater corrosion phenomena [ 20 ]. The SnO 2 layer properties are crucial in determining the interaction of gas with the surface and, consequently, developing new sensors.…”