The impact of r-2,c-6-diphenyl-t-3-methylpiperdin-4-ones with semicarbazone (01SC), r-2,c-6-diphenyl-N-methyl-t-3-ethylpiperdin-4-ones with semicarbazone (02SC) and r-2,c-6-diphenyl-t-3-ethylpiperdin-4-one with semicarbazone (03SC) on the corrosion inhibition nature of mild steel in 1N sulhuric acid is investigated by employing quantum chemical calculation, potentiodynamic polarization, weight loss method and AC impedance spectroscopy methods. The experimental result depicts that the percentage of inhibition efficiency (IE) increases with the rising inhibitor concentration of some alkyl (methyl, N-methyl ethyl, ethyl) substituted piperidin-4-ones with semicarbazone. The adsorption of inhibitor on the mild steel follows the Langmuir adsorption isotherm. The potentiodynamic polarization plots portray that substituted piperdin-4-ones with semicarbazone act as a mixed type character in acid medium. This is suspended by the impedance spectroscopy, which shows a change in the value of charge transfer resistance (Rct) and double layer capacitance (Cdl) indicating the adsorption of the some substituted piperidin-4-ones with semicarbazones on the mild steel surface. Quantum chemical estimations are utilizing Density Functional Theory to identify a transparent link exists that between the inhibiting effect of the inhibitor and the electronic properties of its fundamental constituent.