BROŽEK Vlastimil Vysoká škola chemicko-technologická v Praze

Spoluautoři POKORNÝ Petr, MASTNÝ Libor

This paper deals with the possibility of using different types of phosphate coatings on pre-treated alloy steel standard intended for plasma spraying of ceramics. The task of the phosphate conversion coating is to improve the corrosion resistance of coated steel and simultaneously improved and extended ceramic adhesion to the steel substrate. The selection of the most appropriate phosphate coating (zinc phosphate, zinc-calcium phosphate, manganese phosphate and "three-cations" phosphate coating) was based on the study of the dehydration curves through DTA and TGA analysis with subsequent analysis of morphology, integrity and composition of the coatings after each dehydration step. This was followed by scanning electron microscopy with energy dispersive X-ray spectroskopy. The corrosion resistance of coated samples with different phosphate intermediate layers was verified by measuring of the corrosion potential during spontaneous and discontinuous measurement of polarization resistance in a solution of concentrated H2SO4 and solution of 3wt. % NaCl. The adhesion of coating system for non-alloy steel was validated by pull-off method according to DIN EN ISO 4624 facility COMTEST OP ½ device. Individual samples were placed in closed glove-box under atmospheric condition and tested by spraying of solution of 5 wt. % H2SO4 and 3 wt. % NaCl (i.e. Volvo test). By the method of scanning electron microscopy and energy dispersive X-ray spectroscopy was determined the characteristic of individual fractions.