Indole Hydrazide Derivatives as Potential Corrosion Inhibitors for Mild Steel in HCl Acid Medium: Experimental Study and Theoretical Calculations

Abstract The present work highlights the corrosion inhibition action of two indole-3-hydrazides with varying alkyl chain lengths: 2-(1 H -indol-3-yl)acetohydrazide (IAH) and 4-(1 -indol-3-yl)butanehydrazide (IBH) against mild steel (MS) in 0.5 M hydrochloric acid (HCl) solution using electrochemical gravimetric measurement methods. Both IAH IBH behaved as mixed-type inhibitors, their anticorrosion behaviour was due to a protective film formation on MS surface through physisorption, agreement Langmuir’s adsorption model. morphologies inhibited specimens examined SEM AFM images showed distinctive improvement corrosion. quantum mechanical calculations indicated contribution delocalized ?-electrons indole unit lone-pair electrons carbonyl group for improved studied hydrazides onto metal surface, supporting experimental results. maximum efficiency 80.4 94.1% at 30 °C exposed HCl medium its optimum concentration. better resistance exhibited by system-containing bearing three methylene groups hence having higher molar volume coverage comparison that incorporated only one chemical structure.