Surface Modifications and Corrosion Protection

Corrosion protection systems for Mg alloys

Magnesium alloys are considered as ideal light weight materials due to their high specific strength and good processibility. With ca. 1.8 g/cm³ the density of Mg alloys is less than a quarter of the density of steel, and approximately two-thirds of the density of Al alloys. However, a major drawback for a more intensive use of Mg components is the high susceptibility to corrosion. An efficient way to control corrosion of Mg is given by coatings. The goal of our research in this field is the development of surface pre-treatments to achieve corrosion resistant Mg surfaces. Passivating conversion coatings can act as adhesion promoter for subsequent polymer coatings, and increase the resistance against corrosion and coating undermining and disbonding. A laboratory-scale pre-treatment facility enables to carry out coating experiments under close-to-production conditions, statistical design of experiments is used to determine process parameters. Characterization of the protective coatings and the elucidation of coating formation and/or failure mechanisms is carried out with a high number of different techniques, such as electrochemical impedance spectroscopy, polarization curves, gravimetric determination of hydrogen evolution, weight loss measurements, corrosion tests in test chambers, adhesion tests, and surface analysis.

Corrosion protection on tailored superhydrophobic stainless steel

If the contact between liquid (water) and the material is reduced, it is expected that the corrosion is also reduced. Stainless steel is tailored decreasing the wettability through a low energy self-assembled monolayer, mostly organic acids or silanes. As a pre-treatment the surface morphology may be as well modified. In our research the different characteristic of the coating and of the process are optimized in order to decrease the corrosion rate and at the same it is seek to also decrease the wettability.