Inhibitive action of pipericacid on C38 steel corrosion in HCl solution

5-(1,3-benzodioxol-5-yl)penta-2,4-dienoic acid named piperic acid was obtained by hydrolysis of piperine and characterized by by NMR and IR spectroscopies.Corrosion inhibition effect of piperic acid on C38 steel corrosion in 1 M HCl solutionwas investigated by weight loss method at various temperatures (298 - 353 K).Weight loss measurements indicated that piperic acid decreased the corrosion rate indicating that the natural compound forms a barrier against metal attack in acidic solution; then the efficiency increased with the inhibitor concentrationto attacin 90.4% at 10-3 M. Temperature effect shows that inhibitory actiondecreases to attain 58.3% at 70°C. Activation parameters were evaluated. Piperic acid adsorption accords the Langmuir isotherm. Adsorption free enthalpy was determined and discussed. Attempts to explain 5-(1,3-benzodioxol-5-yl)penta-2,4-dienoic acid (piperic acid: III) were investigated as corrosion inhibitors for mild steel using density functional theory (DFT) at B3LYP/6- 31G(d) level in comparison of piperine(I) and piperanine (II). Quantum chemical parameters most relevant to their potential action as corrosion inhibitors such as EHOMO (highest occupied molecular orbital energy), ELUMO(lowest unoccupied molecular orbital energy), the energy gap(ΔE), dipole moment(μ), electron affinity(A), ionization potential(I), the absolute electronegativity (χ), the hardness (η), the softness(S) and the number of electrons transferred (ΔN) have been calculated and discussed