Extreme Materials

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Quantitative and qualitative insights into the corrosion mitigation mechanism of N,N-dibutyl aniline for mild steel in sulfuric acid

Meenakshi Gupta, Mansi Y. Chaudhary, Neeta Azad, Shramila Yadav

Extreme Materials, 2025, 1(3): 44-60. DOI: 10.1016/j.exm.2025.07.001

Atom	f⁺	f	f²
N1	-0.001	0.15	-0.151
C2	-0.02	-0.047	0.027
C3	-0.027	-0.041	0.014
C4	-0.022	-0.005	-0.017
C5	-0.028	0	-0.028
C6	-0.006	0.021	-0.027
C7	-0.025	0.005	-0.03
C8	-0.024	0.005	-0.029
C9	0.096	0.047	0.049
C10	0.098	0.047	0.051
C11	-0.01	-0.006	-0.004
C12	-0.008	-0.008	0
C13	0.062	0.053	0.009
C14	0.068	0.045	0.023
C15	-0.006	0.061	-0.067
H16	0.022	0.038	-0.016
H17	0.035	0.058	-0.023
H18	0.017	0.041	-0.024
H19	0.042	0.051	-0.009
H20	0.02	-0.012	0.032
H21	0.026	0.029	-0.003
H22	0.023	-0.015	0.038
H23	0.031	0.023	0.008
H24	0.023	0.022	0.001
H25	0.017	0.005	0.012
H26	0.019	0.026	-0.007
H27	0.018	0.003	0.015
H28	0.109	0.032	0.077
H29	0.104	0.037	0.067
H30	0.001	0.011	-0.01
H31	0.02	0.034	-0.014
H32	0.016	0.015	0.001
H33	-0.003	0.016	-0.019
H34	0.021	0.034	-0.013
H35	0.017	0.014	0.003
H36	0.094	0.066	0.028
H37	0.096	0.064	0.032
H38	0.084	0.08	0.004

Table 8 Fukui functions (f^*,f, and f² ) for atoms of NNDBA.

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Fig. 1. Structure of N, N Dibutyl aniline (NNDBA).
Table 1 Temperature and concentration dependent corrosion rate and inhibition efficiency of mild steel in H₂SO₄ medium in the presence and absence of NNDBA determined via gravimetric method.
Fig. 2. Effect of NNDBA concentration on corrosion protection performance of mild steel at all studied temperatures.
Table 2 Time-dependent mass depletion data for mild steel corrosion in H₂SO₄ solution.
Fig. 3. Time-dependent corrosion behavior of mild steel in H₂SO₄.
Fig. 4. Temperature dependence of corrosion rate: logC_r vs. 1/T for mild steel in H₂SO₄ medium in the presence and absence of NNDBA.
Table 3 Energy of activation (E_a ) for mild steel corrosion in H₂SO₄ medium in the presence and absence of NNDBA.
Fig. 5. Different adsorption isotherms for mild steel in H₂SO₄ medium in the presence and absence of NNDBA (a) Langmuir, (b) Freundlich, (c) Temkin, (d) ElAwady, (e) Flory-Huggins, and (f) Frumkin adsorption isotherm.
Table 4 Analysis of adsorption behavior using different isotherm models.
Table 5 Thermodynamic insights from the Langmuir adsorption isotherm at all studied temperatures.
Fig. 6. Temperature dependence of adsorption equilibrium constant: logK_adsvs.1/T.
Fig. 7. Cathodic and anodic polarization run via PDP studies for various concentrations of H₂SO₄ in the presence and absence of NNDBA at 298 K.
Table 6 Corrosion current and inhibition efficiency for mild steel in H₂SO₄ medium in the presence and absence of NNDBA determined via PDP studies at 298 K.
Fig. 8. Bode plot of mild steel in H₂SO₄ and in 10^-1M NNDBA at 298 K.
Fig. 9. Nyquist plot of mild steel in H₂SO₄ and in 10^-1 M NNDBA at 298 K.
Fig. 10. Equivalent Circuit.
Table 7 Electrochemical Impedance parameters for mild steel in H₂SO₄ medium in the presence and absence of NNDBA at 298 K.
Fig. 11. Scanning electron micrograph of mild steel in (a) 0.5H₂SO₄ (b) 10^-1 M NNDBA in H₂SO₄ (c) 10^-7 M NNDBA in H₂SO₄ at 3000 magnifications.
Fig. 12. AFM of (a) plain mild steel specimen, (b) mild steel specimen in the 0.5H₂SO₄ solution (c) mild steel specimen in presence of 10^-1MNNDBAⁱⁿH₂SO₄.
Fig. 13. Optimized geometry of NNDBA with HOMO and LUMO distributions and their corresponding energy levels.
Fig. 14. Optimized geometry of protonated NNDBA with HOMO and LUMO distributions and their corresponding energy levels.
Fig. 15. Bar graph representing the Fukui functions (f^*,f, and f² ) for individual atoms of NNDBA.
Table 9 Outputs calculated by the Monte Carlo simulation for adsorption of NNDBA, on Fe (110).
Fig. 16. MD simulation captures in (a) top view of adsorbed NNDBA molecule on mild steel surface (b) front view of interactions between NNDBA and mild steel (c) top view of adsorbed NNDBA molecule on mild steel in presence of H₂O and H₂SO₄ (d) top view of adsorbed NNDBA molecule on mild steel in presence of H₂O and H₂SO₄.
Table 10 Comparative Overview of NNDBA and Structurally Related Corrosion Inhibitors.
Fig. 17. Visualization of interaction between NNDBA and mild steel (MS) surface.

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