The synergistic effect of dihydroxy benzyl phosphonic acid (DAP) and zinc sulfate ZnSO4 (Zn2+) system in 0.5 M H2SO4 solution on carbon steel X48 has been evaluated using potentiodynamic polarization measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and quantum methods (DFT). The combination of DPA and Zn2+ has been demonstrated to have remarkable inhibitory efficiency (96%). DPA/Zn2+ formulation operate as a mixed inhibitor, inhibiting both the anodic and cathodic reactions to the same amount, according to polarization studies. The diameter of the semicircles increases with the addition of DPA/Zn2+ formulation. Furthermore, the double layer capacitance Cdl decreases and Rt values increase with this combination of DPA and Zn2+, confirming the significant adsorption on the surface steel. The adsorption isotherm of Langmuir is approached by the adsorption on the metal surface. The nature of the protective coating is also determined using surface characterization techniques (FTIR and SEM). The molecular orbital (HOMO and LUMO) energies, energy gap (ΔEgap), dipole moment (μ), global hardness (η), global softness (σ), electrophilicity index (ω), absolute electronegativity (χ) and the fraction of transferred electrons (ΔN) have been determined as supporting evidence.

中文翻译：

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O.5 M H2SO4中二羟基苄基膦酸-Zn2+体系对碳钢的协同缓蚀：实验和理论研究

使用动电位极化测量、电化学阻抗谱 (EIS)、扫描电子显微镜 (SEM)、和量子方法（DFT）。DPA 和 Zn2+ 的组合已被证明具有显着的抑制效率（96%）。根据极化研究，DPA/Zn2+ 配方作为混合抑制剂起作用，将阳极和阴极反应抑制到相同的量。半圆的直径随着 DPA/Zn2+ 配方的加入而增加。此外，双电层电容 Cdl 降低，Rt 值随着 DPA 和 Zn2+ 的组合而增加，证实了在表面钢上的显着吸附。Langmuir的吸附等温线通过金属表面的吸附来逼近。还使用表面表征技术（FTIR 和 SEM）确定保护涂层的性质。分子轨道（HOMO和LUMO）能量、能隙（ΔEgap）、偶极矩（μ）、整体硬度（η）、整体柔软度（σ）、亲电指数（ω）、绝对电负性（χ）和转移分数电子（ΔN）已被确定为支持证据。