The diamond-like a-C:H and a-C:H:W coatings (DLC) were deposited on steel surface by plasma-assisted chem. and phys. vapour deposition methods and then studied for corrosion and tribol. properties after elemental and structural anal. In friction pairs operating under thy friction conditions, the elements coated with DLC showed better tribol. properties than the uncoated elements. After boundary lubrication of the fricting surface with 1-butyl-3-methylimidazolium tetrafluoroborate ionic liq., an increase in the friction properties of the systems was obsd. The presence of W in the amorphous hydrated DLC coatings contributed to an improvement in the tribol. properties of the elements but also to a slight decrease in their corrosion resistance.