PROTECTIVE PROPERTIES OF THE VACUUM ARC DEPOSITED DECORATIVE TiN AND TiO 2 COATINGS ON STAINLESS STEEL

Recently, the vacuum arc technology was developed for the deposition of the decorative and protective titanium nitride and titanium dioxide coatings on large area substrates. An industrial installation "Nikolay" for vacuum arc deposition of decorative and protective coatings is presented. It has the following parameters: size 6000× 3000× 3000 mm, mass 15500 kg, maximum power consumed 75 kW, ultimate vacuum 5× 10 –4 Pa, maximum size of treated strips 2100x1300x8 mm, output capacity for 30 strips 2100× 1300× 5 mm in a cycle and up to 1000 m 2 /month. It allows to deposit titanium nitride coatings having natural golden colour and titanium dioxide coatings having highly uniform interference colours. The morphology and microstructure of the coatings were studied with the aid of atomic force microscopy . Both accelerated tests on atmospheric corrosion and electrochemical tests of itanium nitride and titanium dioxide coatings on the stainless steel substrates were carried out. Hard coatings of refractory metal compounds (Ti, Zr, Cr, Mo, etc.) have more noble properties than steel substrates in an electrochemical sense. Therefore, the deposition of highly-porous nonuniform coatings can even accelerate the corrosion process caused by the formation of a galvanic couple of coating and substrate. It has been shown that the deposited coatings are very dence and have only very scarce individual pores due to the remaining Ti droplets. As a result, the highly decorative and biocompatible TiN and TiO 2 coatings do not deteriorate the corrosion resistance of stainless steel substrates.