EXPERIMENTAL AND THEORETICAL ANALYSIS OF NA OXAZINOQUINOXALINE DERIVATIVE FOR CORROSION INHIBITION OF AISI 1018 STEEL

The inhibitory ability of an oxazinoquinoxaline derivative (OAQX) against the corrosion of AISI 1018 mild steel induced by aqueous 0.6 mol L-1 NaCl solution is herein evaluated. Linear polarization resistance studies showed the inhibitory efficiency of OAQX varying from 62.75% to 75.93% with OAQX concentration ranged from 0.259 x 10-4 mol L-1 to 3.243 x 10-4 mol L-1. Aiming at to investigate the Tafel curves on the OAQX electrochemical behavior at saline (0.6 mol L-1 NaCl) aqueous media the linear Tafel segments of anodic and cathodic curves were extrapolated to the intersection point which afforded corrosion potential (Ecorr) and corrosion current density (icorr) data. By applying Tafel approach the efficiency of OAQX ranges from 55.30% to 87.60%. In both analysis Langmuir isotherm lead to optimized adsorption parameter. The adsorption mechanism of OAQX is proposed from FTIR experiments and quantum calculations. The theoretical employed method is hybrid B3LYP combined with 6-311++G(d,p). Theoretical results showed OAQX as a promising inhibitor that form a stable protective metal-ligand film on metal surfaces, and differs from several heterocyclic compounds due to its solubility in small amount of DMSO (0.627 x 10-4 mol L-1) which is resistant to a saline aqueous media (0.6 mol L-1 NaCl).

本研究评估了一种恶嗪并喹喔啉衍生物（OAQX）对0.6 mol·L⁻¹氯化钠水溶液诱导AISI 1018低碳钢腐蚀的缓蚀性能。线性极化电阻测试结果表明，当OAQX浓度介于0.259×10⁻⁴ mol·L⁻¹至3.243×10⁻⁴ mol·L⁻¹区间时，其缓蚀效率为62.75%~75.93%。为探究OAQX在0.6 mol·L⁻¹氯化钠盐水介质中的电化学行为，本研究将阳极与阴极极化曲线的线性塔菲尔（Tafel）区段外推至交点，由此获得腐蚀电位（Ecorr）与腐蚀电流密度（icorr）相关数据。采用塔菲尔外推法计算得到的OAQX缓蚀效率为55.30%~87.60%。两种分析方法均表明，朗缪尔吸附等温式（Langmuir isotherm）可得到最优吸附参数。结合傅里叶变换红外光谱（FTIR）实验与量子化学计算结果，本研究提出了OAQX的吸附缓蚀机制。理论计算采用杂化泛函B3LYP结合6-311++G(d,p)基组的计算方案。理论计算结果显示，OAQX是一种性能优异的缓蚀剂，可在金属表面形成稳定的保护性金属-配体保护膜；且与多数杂环类化合物不同，其在少量二甲基亚砜（DMSO）中的溶解度可达0.627×10⁻⁴ mol·L⁻¹，且该缓蚀剂在0.6 mol·L⁻¹氯化钠盐水介质中稳定性优异。