This study set out to determine the effectiveness of birch leaves extract (BLE) as a corrosion inhibitor against X52 pipeline steel in the pickling solution. Chemical and electrochemical techniques, as well as scanning electron microscope (SEM), Fourier-transform infrared (FT-IR), and adsorption isotherms were used in the research. Various triterpenoids, including betulin, betulinic acid, oleanolic acid, sitosterol, and kaempferol, are unquestionably involved in the corrosion inhibition mechanism, according to the high-performance-liquid-chromatography (HPLC) analysis. The 95% efficiency of the produced BLE extract (at optimum concentration 400 mg L−1) significantly reduced the corrosion rate of X52 pipeline steel in the pickling solution. The adsorption of BLE extract molecules on the X52-steel surface was demonstrated by SEM and FT-IR analysis. The adsorption activity follows the Langmuir adsorption theory.