目的 开发一种绿色缓蚀剂，并研究它对碳钢在酸性溶液中的缓蚀作用及机理。方法 用体积分数为70%的乙醇水溶液回流获得长春花提取物(CR-E)，通过失重实验、电化学综合实验、火焰原子吸收分光光度法(FAAS)、傅里叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)等分析CR-E对Q235碳钢在0.5 mol/L H2SO4溶液中的缓蚀性能和机理。结果 CR-E对Q235碳钢在H2SO4溶液中的腐蚀具有良好的缓蚀效果，缓蚀效率随着CR-E浓度的增加而增大，在CR-E的质量浓度为1 000 mg/L时，缓蚀效率达到89.84%。添加CR-E后可迅速抑制腐蚀，并持续发挥缓蚀作用，在浸泡48 h后Q235碳钢的缓蚀效率仍可达89.99%;电化学综合实验结果表明，CR-E是一种有效的混合抑制型缓蚀剂，腐蚀反应的电荷转移电阻随着CR-E浓度的增加而增大，腐蚀电流密度则随之减小;通过FAAS证实阳极铁的溶解被抑制，通过FTIR证实CR-E分子可以有效吸附在Q235碳钢表面，通过SEM证实Q235碳钢表面受到了CR-E的有效防护。缓蚀机理是CR-E缓蚀剂分子在Q235碳钢表面的吸附减缓了铁在腐蚀溶液中的溶解，腐蚀过程受到显著抑制，该吸附以物理吸附为主，且遵循Langmuir吸附等温模式。结论 在0.5 mol/L H2SO4溶液中，CR-E对Q235碳钢的缓蚀作用显著，可作为一种候选绿色缓蚀剂在工业领域推广应用。

The work aims to develop a new green corrosion inhibitor and find its corrosion inhibition effect on Q235 carbon steel in acidic solution. Catharanthus roseus extract (CR-E) was obtained by reflux extraction with 70% ethanol aqueous solution. The corrosion inhibition performance and mechanism of CR-E on Q235 carbon steel in 0.5 mol/L H2SO4 solution were assessed by classical weight loss experiment, electrochemical comprehensive experiment, flame atomic absorption spectrometry (FAAS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The weight loss experiment showed that CR-E had a good corrosion inhibition effect on Q235 carbon steel in 0.5 mol/L H2SO4 solution. The corrosion inhibition efficiency increased with CR-E concentration to attain 89.84% at 1 000 mg/L at 298 K. After CR-E was added, it could quickly retard corrosion and continue to exert a corrosion inhibition effect. The corrosion rate of Q235 carbon steel containing CR-E was 21.56% of that in the blank one after 3 h exposure and 8.57% after 24 h exposure. The corrosion inhibition efficiency could still reach 89.99% after soaking for 48 h in 0.5 mol/L H2SO4 solution. Adsorption of CR-E on the surface of Q235 carbon steel followed Langmuir adsorption isotherm and was spontaneous. The strong physisorption and weak chemisorption were involved according to the standard Gibbs adsorption free energy ( = –25.81 kJ/mol). According to the findings of the polarization curves, the CR-E performed as an effective mixed-type inhibitor. The parallel cathodic branch revealed that the mechanism of the hydrogen evolution was not affected by the addition of CR-E in H2SO4 solution. The inhibition efficiency calculated by the corrosion current density and polarization resistance increased and went up to 95.54% and 94.22% at 500 mg/L CR-E concentration respectively. A single capacitive loop and only one time constant were observed from electrochemical impedance spectroscopy (EIS), which indicated that the mechanism of the charge transfer process of metal dissolution was unchanged by the presence of CR-E. The enhanced charge transfer resistance of corrosion reaction with increasing CR-E concentration was revealed, and the inhibition efficiency was 89.52% at 500 mg/L CR-E concentration by the EIS parameters from the equivalent circuit analysis. The concentration of Fe was only 7.24% of that in the blank solution by the FAAS analysis, which confirmed that the dissolution of anode iron was inhibited. The similar adsorption peaks of FTIR spectra of CR-E and the CR-E adsorbed layer on Q235 carbon steel surface confirmed that CR-E molecules with N and O groups could be effectively adsorbed on the surface of Q235 carbon steel. SEM microscopy analysis of Q235 carbon steel samples reveals that the degradation rate of carbon steel is significantly lowered and CR-E provides effective protection. The inhibition mechanism of CR-E is mainly attributed to the adsorption of protonated CR-E molecules by electrostatic attraction or coordinate bonds blocking the active site of the corrosion. CR-E has significant corrosion inhibition properties by the adsorption of functional groups on carbon steel in 0.5 mol/L H2SO4 solution, and can be used as a green corrosion inhibitor candidate in the industry.