介质pH对银基上4-甲基-4H-3-巯基-1,2,4-三氮唑成膜结构和缓蚀性能影响的SERS和电化学研究

The pH effect on the structure and corrosion properties of 4-Methyl-4H-1,2,4-triazole-3-thiol film on a silver surface:SERS and electrochemical observations

在不同pH介质中,缓蚀试剂4-甲基-4H-3-巯基-1,2,4-三氮唑(4-MTTL)都能在银基底上形成自组装膜。SERS光谱表明:当pH=3时,4-MTTL分子是以硫醇式,通过两个氮原子为吸附位点,以较平躺方式在银表面构筑自组装膜;当介质为pH=7和pH=11时,4-MTTL以硫醇式,通过氮和硫原子为吸附位点倾斜或垂直方式作用于银表面。由于后者的吸附方式比前者更为垂直于表面,所以形成的膜中分子排列更为致密。电化学极化实验也表明,在pH=3的条件下,形成的4-MTTL单层有更正的腐蚀电位;在pH=11时,构筑的膜缓蚀能力强于pH=7的。并由电化学交流阻抗数据解析了相应的缓蚀机理。

The dilute solution of 4-Methyl-4H-1, 2, 4-triazole-3-thiol （4-MTTL） as a an- ticorrosive reagent, could self-assemble to form film on a silver surface in the solutions with acidic, neutral and alkaline media. The SERS spectra show that when the pH of solu- tion was 3, the 4-MTTL molecule in the thiol form formed film on the silver surface by the two nitrogen atoms in tilted orientation. Moreover, in the case of pH at 7 for the self-as- sembly solution, the film formation of the 4-MTTL in a thiol form onto the silver surface was though the sulfur and nitrogen atoms as adsorption sites with a perpendicular orientation. For pH reaching 11, its adsorption mode was similar to the case of pH 7 but its orientation was more perpendicular comparing with that of the latter, leading that the membrane had higher density. The results of electrochemical polarization exhibited that of the 4-MTTL molecule （pH 3）, corrosion potential shifted positively and it presented the best anticorrosive capability. The monolayers formed the solution with pH 11 presented more anticorrosive than that from the solution with pH 7. Further, electrochemical impedance spectroscopic investigations exploited their anti-corrosive mechanisms.