Experimental studies of the effect of Ti interlayers on the corrosion resistance of TiN PVD coatings by using electrochemical methods

Highlights: • Barrier effect of Ti interlayer is investigated by electrochemical methods. • The Ti interlayer improves drastically the corrosion resistance. • Corrosion on the substrate delaminates coatings with high compressive stresses. • SECM allows the identification of permeable areas with local resolution. - Abstract: The effect of Ti interlayers on the corrosion resistance of TiN PVD coatings is investigated. The coatings were deposited using direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HIPIMS). Ti interlayers with different thicknesses but same composition and deposition parameters were studied. The barrier effect was investigated using potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) together with a chemical porosity test. Remarkable improvement of the corrosion resistance with increased thickness of the Ti interlayers was found. The results showed a good agreement between potentiodynamic polarization tests, EIS, SECM and the microscopic inspection.