Study on the Influence of Three Current Forms on the Cathodic Protection Effect of Pipeline Intelligent Test Piles

In order to explore the influence of different current forms on the protection effect of cathodic protection systems for intelligent test piles of oil and gas gathering and transportation pipelines, X80 steel was taken as the research object to simulate the soil corrosion environment, and cathodic protection performance test experiments were carried out under three current forms: direct current (DC), conventional pulse (P) and high-frequency pulse (HP). Through a polarization curve test, electrochemical impedance spectroscopy (EIS) analysis, surface morphology observation and corrosion rate test, the effects of three current forms on cathodic polarization effect, polarization resistance, corrosion product composition and protection efficiency were compared. The results show that high-frequency pulse current can make the pipeline steel reach the protection potential in a shorter time, and under the same average current density, its polarization resistance is 23.6% and 15.8% higher than that of DC and conventional pulse, respectively. The anti-interference ability of conventional pulse current is better than that of DC. In the presence of stray current, the fluctuation amplitude of protection potential is only 21.1% of DC. The protection stability of DC is good, but the polarization speed is slow, and the phenomenon of “over protection” easily occurs in the process of long-term protection. Combined with economic analysis, high-frequency pulse current has significant advantages in high-corrosion-risk environments. Conventional pulse is suitable for stray current interference areas, while DC is more suitable for long-distance pipeline protection with low corrosion risk. The research results can provide a theoretical basis and technical support for the selection of the current form of pipeline cathodic protection systems.