Inhibition activity of new thiazole hydrazones towards mild steel corrosion in acid media by thermodynamic, electrochemical and quantum chemical methods

Abstract

The mild steel anti-corrosion potential by newly synthesized thiazole hydrazones, 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid benzylidene-hydrazide (TH-1), 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid (3-hydroxy-benzylidene)-hydrazide (TH-2) and 4-(4-methoxy-phenyl)-thiazole-2-carboxylic acid (4-hydroxy-benzylidene)-hydrazide (TH-3) in 0.5M hydrochloric acid was studied by gravimetric and electrochemical techniques. Thermodynamic parameters were evaluated for activation and adsorption processes. Adsorption of the inhibitors followed Langmuir isotherm. Electrochemical measurements showed that addition of inhibitors simultaneously decreased corrosion current density and double layer capacitance but increased charge transfer resistance. Potentiodynamic polarization studies revealed that thiazole hydrazones effectively suppressed both the anodic and cathodic processes of mild steel corrosion in acid solution and hence acted as mixed-type inhibitors. Quantum chemical parameters like EHOMO, ΔE, softness and hardness were very well correlated with experimental data. SEM characterized the film formed on the mild steel.