Effect Study Of Cathodic Protection On Carbon Steel With The Interference Of Stray Current By EIS

Stray current interference is the most severe form of electrochemical corrosion to buried metallic structure. Generally,cathodic protection (CP) has been recognized as the most effective method to protect pipelines from external corrosion in soil. In order to study the effect of cathodic protection on carbon steel with the interference of stray current on the bare carbon steel pipe and pipe with tiny damaged coating,20mA/100mA/200mA DC current and-850mV(CSE)/-1000mV(CSE) cathodic protechtion potential were applied respectively on Q235 carbon steel.AC impedance and linear polarization test were applied on the samples to study the electrochemical performances. The following conclusions were obtained:1.For bare carbon steel pipe, cathodic protection had an inhibitory effect on the DC interference stray current corrosion. Whether there was DC interference individually or DC interference and cathodic protection applied together, the corrosion degree was more and more serious with the increase of interference current value. When cathodic protection was applied individually, the protective effect of situation on -1000mV was better than situation on-850mV.In the presence of constant DC interference, the protective effect of situation on -1000mV was better than situation on-850mV as well. But the protective effect on 200mA DC interference was disappointing when the potential was -850mV (CSE), the polarization resistance equivalent to the value of experiment on 20mA DC.2.For the carbon steel pipe with a small piece of damage on the coating, the cathodic protection also had a protective effect on the samples. In much the same as the effect on bare carbon steel, whether there was existence of DC interference or the DC interference and the cathodic protection applied together, the corrosion degree was also more serious with the increase of interference current value. When cathodic protection was applied individually, the protective effect of situation on -1000mV was better than situation on-850mV. While the cathodic protection potential were-1000mV and-850mV, the protective effect were disappointing on large DC values,such as 100mA and 200mA.