Corrosion behavior of TiN coated steel was studied in terms of thickness of interlayer Ti and TiN coating. TiN was arc ion plated to a thickness of 1$mu extrm{m}$ and 2$mu extrm{m}$ respectively with interlayer coating of Ti of 1$mu extrm{m}$, $2mu extrm{m}$ and $3mu extrm{m}$. Corrosion resistance of TiN coated steel was evaluated by anodic palarization test in 1N $H_2$SO$_4$ as well as salt spray test. Porosity of each coating was also tested by using $SO_2$ test method. Corrosion current density decreased with increasing TiN coating thickness and Ti interlayer coating markedly enhanced the corrosion resistance. Ti interlayer coating of $2mu extrm{m}$ and $3mu extrm{m}$ prior to $2mu extrm{m}$ TiN coating decreased the corrosion current density of active range by an order of 4 and that of passive range by an order of 2. This improvement was associated with the retardation of corrosive agent penetration with increasing coating thickness and inherent corrosion resistance of Ti interlayer. Ti interlayer coating was also very effective in improvement of corrosion resistance under salt atmosphere.