Influencing the Functional Properties of Stainless Steels by Different Surface Treatments

摘要

The corrosion behaviour of stainless steels is dependent on the passive layer. They are formed depending on the alloying composition of the steel, the surface preparation, air humidity, temperature and there is a clearly pronounced time dependence. In this work the passivation behaviour of different kinds of stainless steel was investigated as a function of surface finishing treatments usually performed during production and manufacturing: grinding with several grits of emery paper, pickling with mixtures of nitric and hydrofluoric acids, passivating with nitric acid and chemical cleaning with citric acid. Linear polarization, electrochemical impedance spectroscopy and contact angle measurements were used to investigate the properties obtained thereby. The topography was also analyzed using a white light profilometer. The polarization resistance increases with time of holding in air, but this increase stops after a few days. This was observed even after a chemical passivation treatment. The same influence was observed for the pitting potential: In contrast the influence of surface preparation on surface energy is rather small. The experimental data from impedance spectroscopy, linear polarization measurements, topography and surface energy were used to calculate a surface index which reflects the total contribution of all factors on the functional surface properties.