曼尼希碱疏水基团碳链长度对其缓蚀性能的影响

Effect of Carbon Chain Length of Hydrophobic Group of Mannich Bases on Their Corrosion Inhibition Performance

为了探讨不同碳链长度曼尼希碱的缓蚀性能及缓蚀机理，以丙酮、2-戊酮、2-辛酮为原料与甲醛、二乙胺反应，在pH=2～3下合成了3种不同碳链长度疏水基团的曼尼希碱缓蚀剂[1-二乙胺基-3-丁酮（DEAB）、1-二乙胺基-3-己酮（DEAH）、1-二乙胺基-3-壬酮（DEAN）]；用元素分析仪、傅立叶红外光谱仪（FT—IR）对其结构进行表征；采用静态失重法考察了曼尼希碱分子结构中疏水基团碳链长度对其在15％盐酸中对N80钢缓蚀性能的影响，比较了其在N80钢片表面的吸附行为，并分析了缓蚀机理。结果表明：3种缓蚀剂的缓蚀性能与疏水基团中碳链长度相关，较高浓度下表现很明显；当缓蚀剂含量〈0．6％时，短碳链的缓蚀性能优于长碳链的，缓蚀率大小顺序为DEAB〉DEAH〉DEAN；当缓蚀剂含量≥0．6％时，疏水基团中碳链长度越长，缓蚀性能越好，缓蚀率大小顺序为DEAN〉DEAH〉DEAB，在缓蚀剂含量为1．0％时，DEAN对N80钢的缓蚀率可达98％；3种缓蚀剂在N80钢表面的吸附为自发过程，服从Langmuir吸附等温式，吸附类型是兼有物理吸附和化学吸附的混合型吸附。

Three kinds of Mannich base corrosion inhibitor with different length of carbon chain of hydrophobic groups,including 1-diethylamino-3-butanone(denoted as DEAB),1-diethylamino-3-hexanone(denoted as DEAH) and 1-diethylamino-3-nonanone(denoted as DEAN),were synthesized with acetone,2-pentanone,2-octanone,diethylamine and formaldehyde as the starting materials.The composition and chemical structure of as-synthesized products were characterized by elemental analysis and Fourier transform infrared spectrometry.The corrosion inhibition performance of the three kinds of Mannich base towards N80 steel in 15%hydrochloric acid(HCl) was evaluated by static weight loss method.Moreover,their adsorption behavior on the steel surface was compared,and their corrosion inhibition mechanism was discussed.Results showed that there was correlation between the corrosion inhibition performance of the three kinds of Mannich base and their carbon chain length of hydrophobic groups,and such a correlation became more evident as the dosage of the inhibitors was relatively high.Namely,when the dosage of the inhibitors was below 0.6%(mass fraction;the same hereafter),the inhibitors with shorter carbon chain length of hydrophobic groups exhibited better corrosion inhibition performance,and their inhibition efficiency was ranked as DEAB>DEAH>DEAN.When the dosage of the inhibitors was 1.0%,the inhibition efficiency was 98%.Moreover,the adsorption process of the three kinds of corrosion inhibitors on the surface of N80 steel was spontaneous and followed Langmuir adsorption isotherm,belonging to mixed-type adsorption involving physisorption and chemisorption.