[4-(3-Amino-4-mehoxy-5-methylphenyl)-1-oxo-1H-phthalaz-2-yl] acetic acid hydrazide and its synergetic effect with KI as a novel inhibitor for low carbon steel corrosion in 0.5 M H2SO4

We report the synthesis of novel [4-(3-amino-4-mehoxy-5-methyl phenyl)-1-oxo-1H-phthalaz-2-yl] acetic acid hydrazide (APPH), followed by its characterization using X-ray diffraction (XRD), Fourier transforms infrared (FT-IR) spectroscopy, ¹H-NMR spectroscopy, and LC/MS. Further, the inhibition effect of the varying concentration of APPH on the corrosion of low steel (LCS) in 0.5 M H₂SO₄ was investigated by weight loss and electrochemical measurements at 30 °C. The percentage inhibition efficacy of APPH increased with concentration and reached about 84% at 0.5 mM at 30 °C, also rising to 88% after 6 h of exposure. According to the polarization measurements, the investigated APPH works as a mixed-type inhibitor. Furthermore, the synergistic corrosion inhibition mechanism APPH showed that the inhibition efficiency maximizes with increasing inhibitor concentration, and the maximum value was 83% at 0.5 mM APPH. The adsorption of APPH on the LCS surface is more fitting to the Langmuir isotherm model. The free energy value (–ΔG° ads) was 33.3 kJ mol⁻¹. Quantum chemical calculation was applied to APPH and acted as excellent support for the experimental data.

Corrosion Inhibition of Carob Pod Pulp (Ceratonia siliqua L.) on Carbon Steel Surface C38 in Hydrochloric Acid

The effect of C. siliqua pulp corrosion inhibition on carbon steel has been studied by gravimetric testing and electrochemical methods. In this study, two raw extracts were prepared from the pod pulp of C. siliqua: the first is methanolic and the second is aqueous. The UHPLC/DAD analysis indicated gallic acid's presence in the extracts (methanolic and aqueous) of C. siliqua as a major compound. The inhibition results achieved revealed that the aqueous extract with gallic acid had a good anticorrosion activity with an inhibition rate of 91.32% at 3 g/l for a temperature of 323 K. Potentiodynamic polarization was performed in 1 M HCl without and with different concentrations of C. siliqua extracts clearly proves that inhibitor extracts behave as mixed type. Adsorption of this inhibitor for different extracts studied on the surface of the carbon steel obeys Langmuir adsorption with negative values of Δ G ads ∘ , suggesting a stable and spontaneous inhibition process.