极潮湿环境中管道腐蚀防护研究

Research on the Corrosion Protection of Pipeline in Extremely Humid Environment

针对华南某水电厂输水管线因运行环境极为潮湿、表面涂层剥落的情况,采用外加电流阴极保护和涂层联合使用的模拟试验装置,探究阴极保护和涂层联合作用下,碳钢管道的腐蚀机理及不同大小外加电流对管道腐蚀的影响。结果表明:腐蚀初期,施加在样品上的阴极保护电位越负,样品腐蚀速率越低,但随着腐蚀时间的延长,在腐蚀60 d后,处在正常阴极保护电位(-1.20 V≤E≤-0.85 V)(vs SCE,下同)的样品腐蚀速率最低,且过负的阴极保护电位(≤-1.20 V)会造成样品表面涂层的阴极剥离;在正常(-1.20 V≤E≤-0.85 V)和过保护(≤-1.20 V)的阴极保护电位下,样品腐蚀产物较为致密平整,而未施加阴极保护和欠保护阴极保护电位(≥-0.85 V)下,样品腐蚀产物呈细小疏松的颗粒状。

Aiming at the situation of surface coating spalling of water pipeline in a hydropower plant in South China due to extremely humid operating environment,the corrosion mechanism of carbon steel pipelines and the influence of different impressed currents on the corrosion of pipelines under the combined action of impressed current cathodic protection and coating were studied by using the simulation experiment device with the application of both impressed current cathodic protection and coating.Results showed that at the initial stage of corrosion,the more negative the cathodic protection potential applied to the sample,the lower the corrosion rate of the sample.However,with the extension of the corrosion time,the corrosion rate of the sample at the normal cathodic protection potential(-1.20 V≤E≤-0.85 V)(vs SCE,the same below)was the lowest after 60 days of corrosion,and the excessively negative cathodic protection potential(≤-1.20 V)would cause cathodic stripping of the surface coating on the sample.In addition,under normal(-1.20 V≤E≤-0.85 V)and over-protection(≤-1.20 V)cathodic protection potential,the corrosion products of samples were relatively compact and flat.By contrast,under the conditions of no cathodic protection and under-protected cathodic protection potential(≥-0.85 V),the corrosion products of the samples were fine and loose particles.