Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： The effect of strain on the pitting behavior of Q235 carbon steel in solutions of NaHCO3+ NaCl was studied by means of potentiodynamic polarization measurement, EIS and XPS. The results show that in a solution of 0.2 mol稬-1 NaHCO3+0.01 mol稬-1 NaCl, a strain of 8% leads to an obvious increase of the pitting potential Eb of Q235 steel, but as the Cl- concentration increased, the difference between the Eb values of strain and strain free samples decreased. When the Cl- concentration increased to 0.1 mol稬-1, the difference of Eb values disappeared. Besides, strain caused lower impedance, smaller charge transfer resistance Rct and decreased the ratio Fe3+/Fe2+ in the passive film, thereby reduced the stability of passive film. The phenomenon that strain caused the increase of Eb was attributed to that the strain promoted the anodic dissolution of Fe which in turn promoted the preferential adsorption of HCO3- on the surface, as the result the harmful effect of Cl- on the passive film was inhibited. As the ratio HCO3-/Cl- in the solution decreased, the effect of HCO3- decreased and finally disappeared.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： The influence of Cl- concentration and the concentration ratio of HCO3- to Cl- ([HCO3-]/[Cl-]) in NaHCO3+NaCl alkaline solution on the pitting potentials of Q235 carbon steel was studied in a chloride ion concentration range from 0.001 to 0.3 mol/L. It was found that when the Cl- concentration is higher than 0.02 mol/L, good linear relationship exists not only between the pitting potential Eb and [HCO3-]/[Cl-] but also between the meatstable pitting potential Em and [HCO3-]/[Cl-], that is Eb and Em increase linearly with the increase of [HCO3-]/[Cl-]. When the Cl- concentration is lower than 0.02 mol/L, [HCO3-]/[Cl- ] is not linear with Eb and Em, and under these conditions, no micron scale metastable pits can be observed on the steel surface before the occurence of stable pits.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： The adhesion force of several typical coatings on glass fiber reinforced plastics (FRP) and the relevant affecting factors was studied with methods of accelerated corrosion tests, adhesion testing and infrared spectroscopy. The adhesion force between FRP and coatings was related to the roughness and wettability of the FRP surface. The highest adhesion was obtained when the glass fiber clothes outcrop on the FRP surface. The FRP surface being polished with emery paper 240# showed higher adhesion for coatings rather than those with emery papers 60# and 600# respectively. In general, the adhesion of different coatings was related to the polarity of the functional groups in the coatings. Fluorocarbon resin coating which contains halogen- bonds of strong polarity showed higher adhesion. Compared with epoxy coating, both of the polyurethane coating and polysiloxane coating contain not only the ester- and ether-bonds similar to the epoxy coating, but also the urethane-, silicon oxygen- and other polar-bonds, leading to higher adhesion. Results of series comparative tests revealed that after immersion test in 3.5%NaCl solution at 40 ℃ the adhesion force between FRP and coatings decreased faster than those after salt fog test and damp heat test. Correspondingly, the infrared spectroscopy of the tested coatings showed that the molecular degradation in the coatings was more severe after immersion test than after salt fog test.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Corrosion behavior of epoxy coating induced by immersion in real seawater as well as immersion in 3.5%NaCl solution and salt spray in laboratory was characterized by means of electrochemical impedance spectroscopy (EIS). Then the relationship between the electrochemical impedance (|Z |0.01 Hz) of the coating tested in the two laboratory environments and that in seawater immersion test were analyzed. It follows that the degree of corrosion severity of the above three test environments could be ranked as: 3.5%NaCl solution＜seawater immersion＜salt spray. The salt spray test exhibited c.a. 2.3 fold stronger corrosivity for the epoxy coating, or say c.a. 2.3 acceleration effect on the corrosion of epoxy coating in comparison with the real seawater corrosion.
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 Na2MoO4 and triethanolamine (TEA) on pitting corrosion inhibition of Q235 carbon steel was studied with methods of potentiodynamic polarization, microcell potential scanning, EIS and XPS etc. The results show that when Na2MoO4 is compounded with TEA the pitting potential Eb of the steel in 0.02 mol/L NaCl+0.1 mol/L NaHCO3 solution is obviously increased. Under an applied potential of 0.3 V, some potential peaks are observed at active sites on the surface, and the compound of Na2MoO4+TEA can effectively inhibit the number of the active sites and decrease the intensity of the potential peaks. In the solution with Na2MoO4 and TEA, the formed inhibition film on steel surface is composed of mainly Fe2(MoO4)3, Fe2O3 and TEA. The adsorption of TEA may improve the compactness of the inhibition films induced by Na2MoO4 and further increase the inhibition effect.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： The synergistic inhibition effect of MoO42- and NO2- on pitting corrosion of mild steel was studied by polarization curve, electrochemical impedance spectroscopy (EIS), Mott-Schottky plot, and X-ray photoelectron spectroscopy (XPS). The results showed that the metastable pitting potential (Em) and the pitting breakdown potential (Eb) of the mild steel shift significantly to much positive and the value of (Eb-Em) increased markedly when MoO42- and NO2- were applied at the same time, indicating that the combined application of MoO42- and NO2- not only restrained the initiation of metastable pits but also prevented the transition from metastable pits to stable pits, correspondingly where a composite passive film Fe2O3+Fe2(MoO4)3 could form on the mild steel surface. The impedance of the composite passive film Fe2O3+Fe2(MoO4)3 formed in the solution containing MoO42- and NO2- was larger than that of the single passive films formed in the solutions with individual MoO42- or NO2-, while the defects of the former was less than that of the later one, therefore, the composite passive film could provide better protectiveness for the mild steel.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： The Effect of NO2- on the early stages of pitting corrosion of Q235 carbon steel in a simulated concrete pore solution (pH=11) was studied by means of polarization curves, Mott-Schottky curves and XPS methods. It was found that, NO2- inhibits both the stable pitting corrosion and the metastable pitting corrosion. The metastable pitting corrosion potential and the stable pitting corrosion potential increase with the increase of NO2- concentration and follow the similar trend. The nucleation process of pits can apparently be inhibited by a low content of NO2-, however this effect increases only slightly as the NO2- content higher than a critical value about 0.03 mol/L. With the increase of NO2- concentration, more Fe2 + in the passive film can be oxidized into Fe3 + and thereby, the defect density related with oxygen vacancies decreases, so the nucleation process of pits may be inhibited.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： A corrosion resistant coating for AZ91D magnesium alloy was prepared by adding pure magnesium particles, aluminium triphosphate (SAP) and ceria in an epoxy coating. The performance of the coating in 3%NaCl solution was studied with methods of Machu test, electrochemical impedance measurement and scanning electron microscope. The results show that the Mg-rich epoxy coating failed and the magnesium substrate was corroded after immersion for about 2000 h, while no corrosion was observed beneath the coating with SAP and ceria addition after immersion for 4448 h . Distinctly the added SAP and ceria can decrease the activity of magnesium particles in the Mg-rich epoxy and thereby prolong the life time of the coating. On the other hand, the compactness and the barrier property of the coating are improved as well.
Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract：利用电化学阻抗、红外光谱、电镜等方法研究了8-羟基喹啉改善环氧富锌涂层性能的作用。在环氧富锌涂层中用5%的8-羟基喹啉替代锌粉后，锌粉的电荷转移电阻Rct增加，且锌粉/溶液界面双电子层电容Qdl降低，锌粉的反应过程被抑制，因此，虽然锌粉的含量降低了，但是锌粉的阴极保护作用时间却明显延长。另一方面，8-羟基喹啉改性后的环氧富锌涂层的电阻Rc升高，电容Qc降低，涂层孔隙率P降低，涂层的屏蔽性增强。上述两方面的作用，可以显著改善涂层的保护性能，延长涂层寿命。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-08 Cooperative journals: 《腐蚀科学与防护技术》
Abstract：利用加速腐蚀试验、附着力测试、红外光谱分析等手段，研究了几种典型涂层与玻璃钢底材的附着力及其影响因素。玻璃钢与环氧涂层的附着力与玻璃钢表面的粗糙度和润湿性能有关，当玻璃纤维布外露时，涂层附着力最高；240#砂纸打磨表面比60#及600#砂纸打磨表面的涂层附着力要高。不同涂层在玻璃钢表面的附着力与涂层中主要官能团的极性有关，含有极性较弱的碳-碳双键基团的乙烯基漆的附着力较差，而含有极性很强的多卤素键的氟碳树脂漆则表现出了较强的附着力。对比高温浸泡试验、盐雾试验和湿热试验的结果，高温浸泡试验对涂层附着力降低的影响更大；红外光谱分析表明高温浸泡与盐雾试验相比涂层内部的分子降解程度更明显。
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