Investigation of the influence of Mg on the corrosion behavior of hard coated steel substrates

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The renewal proposal enhances and focuses the aims of the running project with regard to intermediate results and hypotheses. Out of this three major aims are conducted.At first the predicted corrosion protection model will be finally verified by electrochemical methods and the influencing factors on the corrosion behavior (area ratio, chemical and structural coating properties) will be correlated to the efficiency of magnesium in the coating. This knowledge in combination with electrochemical behavior of magnesium in the corrosion system enables a specific development of hard coating systems with enhanced corrosion performance.Secondly the reason for the worse corrosion behavior of coatings from application-relevant mixed-target deposition will be investigated by electrochemical methods and structure analysis. From this investigations information to the binding state of magnesium and the influence of nitrogen content on the corrosion behavior should be derived. This is a prerequisite for the optimization of the coating procedure to produce application-relevant and corrosion resistant PVD-hard-coatings on steel.The third aim is the development of a short-time testing method based on the combination of electrochemical and optical investigation techniques for the evaluation of the corrosion protection efficiency. After an adaption of testing parameters this methods enables the qualitatively and quantitatively characterization of the coatings by means of electrochemical parameters and statistical evaluation of indicated defects. Furthermore a direct correlation to the coating defects becomes possible which enhances the development of more corrosion resistant coatings. Compared to the conventional salt spray testing a better meaningfulness, sensitivity and efficiency can be expected.The achieved results in the renewal project should enhance the understanding of the corrosion protection mechanism as well as influencing factors initiating corrosion and controlling its kinetic. The application potential of these new hard coatings can be estimated and the findings can be used for the future development of corrosion resistant hard coatings.