Two tripodal pyrazolic ligands: application against corrosion of mild steel in HCl 1M

Two tripodal pyrazolic ligands: N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methy)-2,4-difluoroaniline ( 2Fpyr 1 ) and N,N-bis((1H-pyrazol-1-yl)methyl)-2,4-difluoroaniline ( 2Fpyr 2 ) were synthetized in good yiels. Then we applied them against corrosion of mild steel in HCl 1M solution. Weight loss measurement give us the inhibition efficiencies values reached 80.2 % for 2Fpyr1 and 77.3 % for 2Fpyr 2 at the concentration 10 -3 , then by changing the temperature from 313K to 343 K, which give us the activation and adsorption parameters, and we reveal from it that the ligands 2Fpyr 1 were adsorbed according to Langmuir Isotherm, but 2Fpyr 2 were was adsorbed according to El-Awady adsorption Isotherm, we obtain these results using certain isotherms as Langmuir, Freundlich, Temkin, Frumkin, Florry-Huggins, Adejo-Ekwenchi and El-Awady. We conclude from polarization curves that all the ligands are mixed type inhibitors (anodic and cathodic type inhibitors), and from the impedance diagrams in the Nyquist presentation which are in the form of one half loop because that the corrosion is controlled by charge transfer process. We used GAUSSIAN 09W program to do theoretical investigations by considering the Density Functional Theory (DFT) method to calculate quantum parameters as E HOMO , E LUMO , ∆E HOMO -E LUMO and μ dipolar moment that allows us to confirm experimental results obtained from gravimetric and electrochemical studies.