TiN Coatings Modified by an Interlayer of Electroplated Chromium on Mild Steel

TiN films on mild steel were deposited by reactive d.c. magnetron sputtering: electroplated chromium was incorporated as an interlayer. Surface hardness, measured by the Knoop indentation method under a load of 25 gf, phase analysis by the X-ray diffraction method and corrosion behaviour by the potentiodynamic measurement technique of these coatings have been evaluated. Surface hardness values were found to increase from about 1000–1100 for TiN coatings on mild steel to about 1800–1900 (HK₂₅) for TiN coatings with chromium as interlayer. Potentiodynamic corrosion tests, performed in IN H₂SO₄ solutions, have shown that with a chromium interlayer the corrosion resistance increases significantly as compared to TiN only sputtered coatings on mild steel samples. No spoiling of TiN coatings was observed during full sweep voltage of -1000 mV to +1000 mV when they were tested with a chromium interlayer.