The SO2 Test, a Porosity Test for Electroless Nickel and PVD-Coatings/ Der SO2-Test, ein Porositätstest für stromlos aufgebrachte Nickel- und PVD-Beschichtungen

Abstract

Porosity in coatings which are more noble than the substrate can cause catastrophic failures of coated components. This investigation is concerned with the use of the SO 2 test for the evaluation of the porosity of electroless nickel and TiAlN-PVD (Physical Vapour Deposition) coatings on mild steel. Metallography, scanning electron microscopy and glow discharge optical emission spectroscopy techniques were used to evaluate and assess the development of corrosion at defect sites at different test stages. Although nickel is known not to be particularly resistant to SO 2 containing atmospheres, the SO 2 test can be used to assess the porosity of electroless nickel coated specimens in industry as well as for research purpose. The high sensitivity of the SO 2 test makes it, however, impossible to investigate both micropores and larger defects in PVD coatings.