Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： The electrochemical behavior of three solvent- free epoxy coatings on Q345E carbon steel during corrosion-erosion induced by flowing slurry of simulated sea water with 1% (mass fraction) of sand at 60 ℃ was investigated by means of electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM), respectively. The results showed that the flowing slurry induced erosion aggravated the deterioration of coatings. The amine-cured epoxy powder coating and phenolic aldehyde amine-cured liquid epoxy coating were cured with slow speed and thus much densified, accordingly, their deterioration process experienced three stages: firstly, the inward migration of corrosive medium; secondly, the corrosion initiation of the substrate metal; thirdly, the corrosion propagation of the substrate metal beneath the coating and finally the failure of coatings. On the contrary, the phenolic aldehyde-cured epoxy powder coating was cured with fast speed and thus much porous, its deterioration process experienced two stages with a shortened second stage. Therefore，the existence of pores in the coating is one of the important factors for inducing failure of coatings during corrosion-erosion.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Three kind of solvent- free epoxy coatings was prepared on 16Mn (Q345E) steel and then their degradation process in flowing artificial sea water 3.5%NaCl solution was investigated by means of gravimetric method, and the acquired weight gain curves were fitted by Fick model. The effect of the flow velocities on the degradation process of coatings was also studied by open circuit potential method (OCP) and electrochemical impedance spectroscopy (EIS). The results showed that, for the amine- cured epoxy powder coating and the phenolic aldehyde- cured epoxy powder coating within the scope of the test flow velocities and the phenolic aldehyde amine-cured liquid epoxy coating at lower flow velocities, the diffusion of water through the coatings by different flow velocities all agreed well with Fick II diffusion model. However, the phenolic aldehyde amine-cured liquid epoxy coating showed irregular regulation by flow velocity 4 m/s, which may be due to aggravated dissolution, thus the diffusion of water through the coating departed from Fick II diffusion model. As the flow velocity increased, the amount of saturated water uptake of the coatings and the water diffusion coefficient increased simultaneously. The degradation processes of the above mentioned three coatings within the scope of test flow velocities may be differentiated as a process of three stages. The increase of flow velocity could accelerate the degradation of the phe-nolic aldehyde -cured epoxy powder coating and the phenolic aldehyde amine-cured liquid epoxy coating, but had little influence on the amine-cured epoxy powder coating.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-10 Cooperative journals: 《中国腐蚀与防护学报》
Abstract：本文通过电化学阻抗谱(EIS)对两种环氧粉末涂层在1.5 mol/L NaCl溶液中的失效行为进行了研究，利用扫描电子显微镜(SEM)和电子发射能谱仪(EDS)对涂层底部金属表面的腐蚀产物进行了分析，探讨了环氧粉末涂层在1.5 mol/L NaCl溶液中的失效机理。结果表明，在1.5 mol/L NaCl溶液中，氯离子等腐蚀介质能在涂层中形成传输通道渗透到达涂层金属界面，并参与界面的腐蚀反应，腐蚀产物主要为铁的氧化物和铁的氯化物。涂层失效的电化学过程可以分为三个阶段：前期、中期和后期。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-09 Cooperative journals: 《中国腐蚀与防护学报》
Abstract：阴极剥离是涂层在水环境(如海水)中失效的主要形式，是涂层/金属界面电化学反应的结果，这说明反应物必须从本体溶液传输到阴极剥离前端区，目前普遍认为水合阳离子沿着涂层金属/界面的传输是阴极剥离的速率决定步骤，所以涂层的抗阴极剥离性能可以用水合阳离子在涂层金属/界面上的表观扩散系数的大小来表征。本文用一种新颖而又简单的方法研究了在0.6mol/L NaCl溶液(60℃)中Na+在一种环氧粉末涂层/金属界面上的传输行为，并建立了数学模型，结果发现实验结果和模型有较好的吻合。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-07 Cooperative journals: 《中国腐蚀与防护学报》
Abstract：通过电化学阻抗谱（EIS）对两种环氧粉末涂层和一种无溶剂环氧液体涂层在60℃流速为2m/s、含1%wt石英砂的3.5%wt NaCl 溶液中的失效行为进行了研究，并利用扫描电镜（SEM）观察了冲刷后涂层的表面形貌，利用激光共聚焦显微镜（CLSM）观察了涂层/金属的断面形貌。结果表明，和静态浸泡相同温度介质条件下相比，流动含砂条件明显加速了无溶剂涂层的失效。冲刷条件下，1#和3#无溶剂涂层由于结构比较致密，失效过程主要分为三个阶段：腐蚀性介质在涂层中传输阶段、基体金属腐蚀发生阶段和基体金属腐蚀发展与涂层失效阶段；2#无溶剂涂层内部由于孔隙较多，涂层较快形成贯穿孔，没有观察到失效中期阶段；涂层体系内部存在孔隙是加速涂层失效的一个重要因素。
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