PVD hard coatings (metals, alloys, nitrides and oxides, carbides) are prepared by vacuum deposition techniques and they are, in many cases, promising alternatives to galvanic protective coating, that they are coming under increasing pressure due to environmental and worker safety issues.
They show a good mechanical, optical and wear properties to compare hard chrome plating. However, corrosion properties of the thin PVD-coatings do not always match all the requirements due to growth-related defects, e.g. pores and pinhols. It is known, that properties of coatings are many-sided related to their microstructure. Therefore, the microstructural characterisation of coatings is extremely important. Many highly effective techniques are available to examine the surface of coatings (SEM, AFM and XPS). The state-of-the-art technique to investigate internal microstructure, sub-surface and the deformation mechanism in coatings is focus ion beam work station (FIB).
In this work PVD coatings (nitrides and metals i.e CrN, Ni, Ni/CrN and Al-W on different substrates were prepared by thermoionic arc ion plating deposition system BAI 730. The corrosion testing of PVD coatings, using electrochemical methods (potentiodinamic data and electrochemical impedance spectroscopy), were performed in chloride medium. Surface and sub-surface characterization were performed before and after corrosion testing by SEM and FIB. Properties such as hardness, roughness and density were determined for each coating. The results are discussed and compared to the surface defects density.
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