阴极电场对楔形缝隙内的屏蔽作用

埋地管道的杂散电流干扰是威胁管道安全的严重问题.为模拟在阴极电场中开裂涂层下管线表面的化学和电化学状况,本文设计了一种模拟涂覆层开裂起翘的楔形缝隙装置,研究了缝口控制电位分别为-776mVSCE和-950mVSCE时的阴极电场中,X-42钢在NS4溶液中楔形缝隙内电位、溶液Cl-离子浓度、Ph值的分布;并比较了相同缝口控制电位下阴极极化状态时,三种参数的分布.结果表明,当缝外有阴极电场时,缝内试片与阴极极化时一样受到电力线分布的影响,但各试片的电极电位远远高于外加阴极极化时的电极电位,Ph值也明显低于外加阴极极化时的情况:阴极电场对本体溶液中的氯离子产生了屏蔽作用,使得溶液中的氯离子很难迁移进缝内,所以越深入缝隙,氯离子浓度越小,变化也越不明显;缝外阴极电场的屏蔽作用在一定程度上抑制了缝隙内自催化反应的进行,达到了一定的保护效果.

Shielding Effect of Cathode Field on the Wedge-Shaped crevice

Interference of stray current is one of the important problems on the safety of the under ground pipelines. To - the chemical and electrochemical conditions under the disbonded coatings on the pipeline, a self -made wedge-shaped simulated crevice was designed to investig- ate the distribution of the potential, the pH value and the concentration of Cl- in the crevice of X-42 pipeline steel in NS4 solution at -776mVSCE, -950mVSCE cathodic electrical field out of the crevice. The same parameters at -776mVSCE, -950mVSCE cathodic polarization were compared. The results showed that because of the effect of the electric-power line, when the crevice in the cathodic electrical field the potential turns less negative compare with it under cathodic polarization and increase with the distance to the mouth of the crevice, the pH value in the crevice turns lower than that under the cathodic polarization and decrease from the mouth to the tip of the crevic, e. As the shielding effect of the cathodic field out of the crevice, it is har- der for the Cl- ion to transferinto the crevice than that under the cathodic polarization. The concentration of Cl- turns lower from the mouth to the tip of the crevice. Shielding effect of the cathodic electric field out of the crevice rejects self-catalysis reaction in the crevice and protects the metal in the crevice in particular degree.