Effects of the sealing process on the corrosion behaviour of thermally sprayed and sealed coatings for corrosion protection of large building parts

摘要

For use as corrosion protection in particularly critical environments thermally sprayed coatings based on Zn, Al and their alloys in combination with one or multiple organic intermediary and cover coats supply many advantages. The subject of the research project described herein is the development of more in-depth knowledge of the influence of sealing process parameters on the corrosion behaviour of the coating system. This objective is reached through an evaluation of common coating characteristics, like the coat thickness, porosity, coat roughness, and adhesive strength. Specifically examined process parameters and determining factors are found in the thermal spraying process itself, the injection parameters and in particular, the sealing process. In order to determine the weak points of the coatings as dependent on the production processes and production parameters, the samples were additionally tested for their corrosion resistance (e.g. lab tests in an artificial atmosphere, electrochemical measuring procedures). An assessment of the coating quality (e.g. thickness, coating defects, presence of residues or pores etc.) after the corrosion tests were carried out. With regard to the sealing process, a significant improvement of the described coating characteristics thus far has been proven in the sealing. Moreover, the surface is evened out. Greater adhesive strength of the coating is evident in the same way as improved corrosion resistance of the coating system. Furthermore, corresponding characteristics were found in the different viscosity settings of the sealing medium. Especially too strong a dilution proves not to be expedient for the corrosion protection effect. The overarching aim of the research work is to develop recommendations at the end of the project for the standardisation process based on the insights gained, so that these can be implemented in practice by the user in the near term.