Abstract: To explore the corrosion law and mechanism of X70 pipeline steel at different pH values, using a potentiodynamic polarization curve and electrochemical impedance spectroscopy, gravimetric method, and X-ray diffraction technology under constant temperature conditions, the electrochemical corrosion behavior of X70 pipeline steel with various pH values in a simulated solution of Qinzhou brick-red soil in Beibu Gulf was investigated.The results show that as the pH value decreases, the capacitive arc resistance value of X70 pipeline steel decreases continuously, the polarization resistance decreases, the self-corrosion potential moves negatively, the self-corrosion current density increases, and the dissolution rate of X70 pipeline steel becomes larger and the corrosion is enhanced.The anode X70 pipeline steel is activated and dissolved during the polarization process, and the cathode reaction includes oxygen absorption corrosion and hydrogen evolution corrosion.More H⁺facilitates the transition of the corrosion products FeO (OH) and Fe₂O₃ to FeO (OH) as the acidity of the solution increases.Furthermore, H⁺will create hydrogen throughout the reaction phase, resulting in loose corrosion products, weakened pipeline steel matrix protection, and worsening corrosion.