Two non-geminine dicationic surfactants containing long chain -dodecyl and heptadecylthio groups were synthesized and their structures were confirmed by spectroscopic methods (FT-IR and NMR). At different concentrations of synthesized inhibitors (5, 25, 50 and 100 ppm) their effectiveness against corrosion of mild steel was investigated by weight loss method for different immersion times (1-4 day) in 1.0 mol L-1 HCl solution. In addition, inhibition efficiencies were investigated in HCl solutions with different concentrations (1.0, 2.0 and 4.0 mol L-1) at 50 ppm inhibitor concentration. While they exhibited good inhibitory properties at all immersion times, they showed the best inhibition activities at 4 days of immersion. In corrosion inhibition tests performed in 2.0 to 4.0 mol L-1 HCl solutions, dicationic surfactant containing dodecylthio group showed higher protection. The critical micelle concentrations of the two synthesized compounds and the surface tension at this concentration were determined, and scanning electron microscopy (SEM) images of metal surfaces were obtained to support the corrosion results.