咪唑啉类化合物在HCl溶液中对碳钢的缓蚀机理分析

Corrosion Inhibition Mechanism of Imidazoline Compounds for Carbon Steel in HCl Aqueous Solution

目的研究咪唑啉(IM)及咪唑啉基脲(IU)在盐酸溶液中对碳钢的缓蚀性能。方法采用静态失重法、电化学测试技术、表面形貌及官能团分析、热力学等温方程等方法,研究缓蚀剂在不同温度的盐酸溶液中对Q235碳钢的缓蚀性能和吸附规律。结果在静态失重试验中,室温下,随着IM、IU缓蚀剂的加入,碳钢的腐蚀速率从12.54 mg/(cm^2·h)分别降低到5.132、0.145 mg/(cm^2·h),IM、IU的缓蚀率分别为59.1%和98.9%。随着温度的升高,缓蚀效率略有下降。极化曲线试验表明,增加两种缓蚀剂的浓度,腐蚀电位负移,阳极电流密度下降明显。交流阻抗的测试显示,随着两种缓蚀剂浓度的增大,拟合参数Rct增大、Cdl减小,证明缓蚀剂在金属表面取代了水,并吸附成膜。研究等温吸附模型发现,两种缓蚀剂分子在碳钢表面的吸附符合Langmuir等温吸附方程,且根据SEM及XPS分析,证明缓蚀剂分子通过N原子与金属形成共价键,在金属表面吸附成膜。结论咪唑啉和咪唑啉基脲对碳钢均具有缓蚀效果,且咪唑啉基脲的缓蚀效果更优异。两种缓蚀剂均属于混合型缓蚀剂,且以抑制阴极腐蚀反应速率为主。两种咪唑啉化合物在碳钢表面的吸附过程为自发放热过程,其吸附规律遵循Langmuir吸附等温模型,属于单分子层吸附。

The work aims to investigate the corrosion inhibition of imidazoline(IM)and imidazolidinyl urea(IU)for carbon steel in HCl solution.Weight loss method,electrochemical technique,surface analysis,functional group analysis and thermody namic isothermal equation were used to study corrosion property and adsorption rule of corrosion inhibitors for Q235 carbon steel HCl solution at different temperature.In the weight loss test,as the corrosion inhibitor(IM,IU)was added at ambient temperature,the corrosion rate decreased from 12.54 mg/(cm^2·h)to 5.132 and 0.145 mg/(cm^2·h)respectively and the corrosion inhibition rate of corrosion inhibitors was 59.1%and 98.9%respectively.Furthermore,the corrosion inhibition efficiency decreased with the increase of temperature.From polarization curve test,the corrosion potential of two corrosion inhibitors was moving forward and the cathode current density decreased obviously as concentration increased.From the alternating current resistance test,with the increase of concentration,of the fitted parameter Rct increased and Cdl decreased.The corrosion inhibitors replaced water on the metal surface and were adsorbed to the film.The adsorption of the two corrosion inhibitors on metal surface obeyed the Langmuir isothermal adsorption equation.According to SEM and XPS analysis,the molecules of corrosion inhibitors could form covalent bonds with metal by N atom and could be adsorbed to the film on the metal surface.IM and IU have corrosion inhibition effects on carbon steel and IU has stronger inhibition effect.Both corrosion inhibitors are mixed type corrosion inhibitors and have high corrosion resistance to the cathode.The adsorption of these two compounds on the surface of carbon steel is spontaneous exothermic process and the adsorption rules are in accordance with the Langmuir isothermal adsorption which belongs to single molecular layer adsorption.