Magnetron Sputtered TiN Coatings Modified by Chromium, Nickel and Electroless Nickel (EN) Interlayers on Mild Steel

Abstract

TiN films were deposited by reactive d.c. magnetron sputtering on mild steel substrate. Because of presence of inherent porosity and internal stresses, TiN coatings cannot be relied to give corrosion protection; also TiN coatings need a good load support. Electroplated chromium and nickel and electroless nickel (EN) were deposited by plating as interlayers below the TiN coatings to study comparatively the effect of these interlayers. Chromium was electrodeposited from conventional sulfate catalysed chromic acid bath and nickel using Watt's bath while EN by electroless deposition process using acidic hypophosphite bath. Three different thicknesses viz. 2, 4 and 10 μm of interlayers were employed to study their influence on TiN coatings. The corrosion behaviour of TiN coated mild steel samples with and without the interlayers was studied using potentiodynamic measurement technique in deaerated IN H₂SO₄ electrolyte. It was observed that TiN coatings on mild steel without any interlayer almost mimic the behaviour of the substrate, while the presence of any of the three interlayers showed a considerable improvement in the corrosion resistance.

Keywords::

• Magnetron sputtering
• Titanium nitride
• Chromium
• Nickel
• Electroless nickel (EN)
• Interlayers
• Corrosion test