This research includes synthesis of new 5-Nitro isatin derivatives starting from 5-nitro-3-(imino acetohydrazide)-2-oxo indole (1) namely 5-nitro-3-[iminoaceto(tetra hydropyridazin-3,6-dione)-2-yl]-2-oxo indole (2); 5-nitro-3-[iminoaceto(hexahydrodiazepine-3,7-dione)-2-yl]-2-oxo indole (3); 5-nitro-3-[iminoaceto (1,2-dihydro pyridiazin-3,6-dione)-2-yl]-2-oxo indole (4); 5-nitro-3-[iminoaceto (8-nitro-1,2-dihydrophtalazin-3,10-dione)-2-yl]-2-oxo indole (5) and 5-nitro-3-[iminoaceto (1,2-dihydrophtalazin-3,10-dione)-2-yl]-2-oxo indole (6). The derivatives were characterized using FTIR, 1 HNMR, 13 CNMR and C.H.N.S analysis with the measurement of some physical properties. Quantum mechanical method of the Density Functional Theory (DFT) of B3LYP with a level of 6-311++G (2d, 2p) were used to calculate the geometrical structure, physical properties and inhibition efficiency parameters, were at the equilibrium geometry in four media (vacuum, DMSO, EtOH and H 2 O). The theoretical results showed that compound (3) was the best corrosion inhibitor among the others. Finally, the corrosion inhibition, kinetics, and thermodynamics studies of the prepared compound (3) for carbon-steel in sea water had been conducted using the potentiodynamic polarization procedure, while the surface changes of the carbon steel were studied using SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy) techniques.