To improve the resistance of carbon steel to corrosion in hostile settings, corrosion inhibitors are often applied to the steel. Both triethyl-hexyl-ammonium bromide (THAB) and dodecyl-triethyl-ammonium bromide (DTAB), which are cationic surfactants based on ammonium, were synthesized, described, and evaluated as potential corrosion inhibitors for API X-65 type steel in oil wells formation water under H2S conditions. Due to the fabrication of inhibitive film, the anti-corrosion properties of the carbon steel are significantly enhanced in the presence of organic corrosion inhibitors. In order to verify the THAB and DTAB chemical structures, a number of different spectroscopic methods such as FTIR and 1HNMR were utilized. Both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were utilized in this investigation to determine the effectiveness of the selected chemicals in inhibiting corrosion. The efficiency reached 81% for compound THAB and 82% for compound DTAB at 250 ppm It was revealed that the concentration of the inhibitor as well as the length of the spacer in their chemical structure both had an effect on the inhibition effect. Quantum chemical calculations and Monte Carlo simulation techniques were used to support the obtained experimental results.