Three Gemini cationic surfactants (GI-surfactants) of different hydrophobic chain lengths based on di-imine compound, abbreviated as GI-6, GI-12 and GI-14, were synthesized and characterized using FT-IR and 1HNMR. The surface-active parameters calculated in acidic media were discussed. The inhibition performance of GI-surfactants for X65-steel corrosion was assessed by weight loss and electrochemical techniques in 1M HCl and was accompanied by surface analysis and theoretical studies. The resistance of X65-steel was enhanced to nearly ⁓764 ohm.cm2 after adding 1x10-3 M of GI-14. This inferred a protective film formation on the X65-steel surface via adsorption phenomena that followed the Langmuir isotherm. The GI-surfactants' inhibition efficiency exceeded 95% at room temperature and 93 % at 328 K owing to the electron-rich centers' presence in their chemical structures. The relation between the prepared GI-surfactants molecular structures and their corrosion inhibition performance was studied theoretically based on DFT and MCs methods. The safeguard effect of GI-surfactants was confirmed by SEM and EDX. The comparison study between the GI-surfactants' performance and the previously reported compounds confirmed their high potential applications as corrosion inhibitors.