Electrochemical and quantum chemical studies on phthalhydrazide as corrosion inhibitor for mild steel in 1 M HCl solution

Abstract

The inhibition ability of phthalhydrazide (PTD) for mild steel in 1 M HCl at 30°C was investigated by electrochemical measurements [impedance spectroscopy (EIS) and potentiodynamic polarization techniques] and quantum chemical calculations. The frontier molecular orbital energy E HOMO (highest occupied molecular orbital), E LUMO (lowest unoccupied molecular orbital), and the Mulliken charge distribution were calculated and are discussed. Results showed that the inhibition efficiency of PTD increased with inhibitor concentration. The maximum corrosion inhibition efficiency was 77.6% at 2 mM PTD. Adsorption of the inhibitor followed the Langmuir adsorption isotherm. Adsorption of inhibitor molecules on mild steel surface occurred spontaneously and chemically. Quantum chemical calculations showed that the low performance of PTD as a corrosion inhibitor is due to the large energy gap (E HOMO -E LUMO ).

Phthalhydrazide nanoparticles as new highly reusable organic photocatalyst in the photodegradation of organic and inorganic contaminants

“…When PHD was added to MO solution, the latter molecules can be only a little adsorbed via hydrogen bonding on the surface of PHD in the absence of irradiation. Moreover, considering the large energy gap ( E HOMO – E LUMO ) of PHD, it cannot undergo a redox reaction with other compounds in the absence of light. Therefore, excitation of electrons from HOMO to LUMO can be achieved under irradiation.…”

Evaluation of Eulychnia acida and Echinopsis chiloensis (Cactaceae) extracts in inhibiting corrosion of carbon steel in HCl solution

“…[6,7] Most organic compounds currently used as corrosion inhibitors have in their structure heterocyclic systems, containing N, S, and O atoms; as well as polar groups, such as -OH and -NH 2 ; and double/triple bonds. The presence of heteroatoms and electrons play an important role in the adsorption of these compounds on the metallic surface [8][9][10][11][12] by interactions between nonbinding electrons and/or π electron clouds of the donor atoms to the metal surface, thus reducing the corrosion attacks. Although many of these compounds have high inhibition efficiencies, they may also present high operating costs or side effects; even in small concentrations, they may be toxic to humans or harmful to the environment.…”