目的：研究4-苯基氨基硫脲（4-PTC）对Q235钢在1mol/L HCl中的缓蚀作用。方法采用异硫氰酸苯酯和水合肼为原料，合成4-PTC。采用熔点分析、核磁共振氢谱和红外光谱等方法确定合成物质为目标产物4-苯基氨基硫脲。采用静态失重法、电化学极化曲线法、电化学阻抗谱法和扫描电子显微镜法，分析研究4-PTC的缓蚀性能。结果静态失重实验表明，当4-PTC浓度增加到1.0 mmol/L时，缓蚀效率达到85.9%，在Q235钢表面吸附符合Langmuir吸附等温式，形成单分子吸附层。计算得到吉布斯自由能为-35.60 kJ/mol，说明缓蚀剂分子在Q235钢表面吸附同时存在物理吸附和化学吸附过程。动电位极化曲线表明，该缓蚀剂是以阴极型为主的混合型缓蚀剂，当4-PTC浓度增加到1.0 mmol/L时，缓蚀效率达到83.6%。电化学阻抗谱表明，随4-PTC浓度的增加，电荷转移电阻值增大，双电层电容值减小，金属腐蚀速率降低，缓蚀作用增强。当4-PTC浓度增加到1.0 mmol/L时，缓蚀效率达到84.7%。扫描电子显微镜表明，缓蚀剂分子能有效保护金属表面，抑制腐蚀。结论在盐酸介质中，4-PTC对Q235钢具有优良的缓蚀性能。
ABSTRACT:Objective To investigate the inhibition performance of 4-Phenylthiosemicarbazide (4-PTC) for Q235 steel in 1 mol/L HCl solution.MethodsA new corrosion inhibitor, 4-PTC, was synthesized using phenyl isothiocyanate and hydrazine hydrate as raw materials. The synthesized compound was confirmed by melting point, 1H-NMR and IR methods. The corrosion inhibition efficiency of 4-PTC was measured by weight loss, potentiodynamic polarization, electrochemical impedance spec- troscopy and scanning electron microscope methods.ResultsThe results of weight loss measurements showed that the inhibi-tion efficiency of 4-PTC could reach up to 85.9% at the concentration of 1.0 mmol/L and the adsorption process obeyed the Langmuir adsorption isotherm, forming monolayer. The value of ΔGads was-35.60 kJ/mol, which indicated that the adsorption mechanism involved both chemisorption and physisorption. The potentiodynamic polarization plots showed that 4-PTC acted as a mixed type inhibitor and showed more pronounced influence in the cathodic polarization plots compared to that in the anodic plots. The inhibition efficiency of 4-PTC could reach up to 83.6% at the concentration of 1.0 mmol/L. Meanwhile, the electro-chemical impedance showed that the charge transfer resistance increased with the increase of the 4-PTC concentration, while the value of double layer capacitance decreased. This phenomenon showed that the corrosion rate decreased and the inhibition effi-ciency increased. The inhibition efficiency of 4-PTC could reach up to 84.7% at the concentration of 1.0 mmol/L. The scanning electron microscope method showed that the 4-PTC had excellent inhibition behavior and could protect the Q235 steel.Conclu-sion4-PTC showed good inhibition efficiency for Q235 steel in HCl solution.
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