Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: Effect of hydrostatic pressure on the electrochemical corrosion of X100 pipeline steel in 0.5 mol/L NaHCO3+0.03 mol/L NaCl solution was investigated by means of methodspotentindynamic polarization, electrochemical impedance spectroscopy and Mott-Schottky. The results show that with the increasing hydrostatic pressure the number and the size of corrosion pits increase, while the activity of ions in the solution also increases, which in turn promotes the adsorpting of Cl- in the passive film. As a result, the corrosion rate and the corrosion current density are increased. The component of the passive film transforms from oxide or hydroxide formed by low pressures to carbonate by high pressures, which may result in the decrease of corrosion-resistance and increase of probability of pitting corrosion nucleation. The passivation film formed on the X100 steel exhibits characteristics of n-type semiconductor. The increase amount of Cl- in the passivation film promotes the increase of lattice imperfections and facilitates the cracking of the oxide film.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The corrosion behavior of X70 pipeline steel in a near-neutral pH solution NS4 with and without sulfate-reducing bacteria (SRB) respectively was studied by means of electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and microscopic observation. The results showed that the corrosion rate of X70 steel increased with time in NS4 solution without SRB; The growth process of the SRB in the solution NS4 can be divided into three phases: logarithmic phase (1~3 d), stable growth phase (4~7 d) and death phase (7~14 d). The influence of SRB on the corrosion rate of X70 pipeline steel in the solution NS4 with SRB was related to the growth process of SRB. A compact biological film could form on the steel surface in the stage of logarithmic phase and stable growth phase, which was conducive to enhancing the protectiveness of corrosion products on the steel and therewith the corrosion rate of X70 steel in the NS4 with SRB was lower than that without SRB. While the corrosion of X70 steel in the NS4 with SRB in the death phase was more serious than that without SRB, while the scale of corrosion products became thicker gradually, then the biological film broken and therewith the corrosion rate increased.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: The electrochemical corrosion behavior of hydrogen- charged base metal and welded joint of X80 pipeline steel in a near-neutral solution was studied by means of potentiodynamic polarization and electrochemical impedance spectroscopy. The morphologies of the base metal and the welded joint of X80 pipeline steel were observed by optical microscopy and the content of released-hydrogen were measured, respectively. It was found that charged-hydrogen had little effect on the microstructure of X80 pipeline steel. The hydrogen content of the welded joint is higher than that of the base metal under the same hydrogen charging condition. The base metal demonstrated higher corrosion resistance than the welded joint when they were not hydrogen charged. However, the charged hydrogen facilitated the anodic dissolution of the base metal and the welded joint of X80 pipeline steel, and the corrosion were accelerated in the near-neutral solution with the increase of charging time. Due to pinning effect on the hydrogen induced by the higher concentration of dislocations defects, the welded joint showed better corrosion resistance than that of the base metal.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A new imidazoline inhibitor was synthesized using 1-methylimidazole, 1,4-butane sultone and concentrated sulfuric acid as raw materials and then of which the corrosion inhibition on X100 pipeline steel in 5%HCl was examined by means of weight loss method and electrochemical technology. The results showed that the inhibitor is a mixed type inhibitor. The inhibition efficiency increased with the increasing inhibitor concentration, while decreased with the increase of temperature. The activation energy of corrosion and the relevant thermodynamic parameters such as enthalpy, entropy, adsorption equilibrium constants and standard free energy ect were acquired so that to reveal the mechanism of corrosion inhibition. The results showed that the corrosion inhibitor was physically adsorbed on the X100 steel surface.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Effect of temperature on corrosion behavior of X70 pipeline steel in high pH solution (0.5 mol/L Na2CO3+0.5 mol/L NaHCO3) was studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy and Mott- Schottky measurements. Results showed that the pitting potential, passive current density and the polarization resistance of X70 pipeline steel all decreased with the increase of temperature. In the experimental temperature range, the formed passive film consisted mainly of Fe2O3 and Fe3O4 with features of n-type semiconductor. With the rising temperature, the thickness and donor density of the passive film increased, correspondingly, corrosion tendency of the steel increased. Therefore, the stability of the passive film decreased with the increasing temperature, which weakened the corrosion resistance of the X70 steel.