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: 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.