Corrosion Inhibitory Studies of Novel Schiff Bases Derived from Hydralazine Hydrochloride on Mild Steel in Acidic Media

The inhibition performance of 1-hydralazinophthalazine (HPZ) (1), and synthesized1-(2-[(5-methylfuran-2-yl)methylene)] hydrazono) phthalazine (MFHPZ) (2), 1-(phthalazin-1(2H)-one) [(pyridin-2-yl) ethylidene] hydrazone (ACPHPZ) (3) and (2-acetylthiophene hydrazono) phthalazine (ACTHPZ) (4) has been investigated for mild steel in 1 M HCl. Compound 4 shows maximum inhibition efficiency of 93% at 5.0 × 10-3 M concentration. The evaluation of thermodynamics and activation parameters indicated spontaneous adsorption of the inhibitor molecules which takes place through chemisorption. The adsorption of 3 and 2 follows Langmuir adsorption isotherm and Temkin adsorption isotherm for 4 and 1. The inhibitor efficiency was of the order 4 > 3 > 1 > 2. Impedance study for the representative inhibitor compounds 4 and 3 showed that decrease in charge transfer resistance is responsible for effective protection of mild steel surface by the tested inhibitor.