Electrophoretic acrylic paints with different colour pigments concentrations

摘要

The aim of this work is the study of the cathodic electrodeposition of a waterborne acrylic binder in presence of different colour pigments considering the effect on the properties of the coated panels in function of accelerated and natural exposure. The first step is the individuation of the suitable deposition parameters in order to obtain a protective coating layer without the pigments. Then, 3 different colour pigments were introduced. Red pigment (organic nature), white one (inorganic nature) and black one (carbon black) were added in 3 levels of concentration (0.5, 1 and 1.5% wt.). The film thicknesses were found about 20 μm. The coatings showed good corrosion protection properties. The magnitudes of the |Z|_(0.01Hz) remained in the order of 10~(11) Ohmcm~2 for about two weeks of immersion in sodium chloride solution. The samples are exposed to UV-B radiation for 500 hours (ASTM G154 Standard). Finally in the natural weathering the colour painted samples were exposed in a site near Trento (alpine region, north of Italy) for 1 year. The change of color and gloss were measured. The produced damage was evaluated by microscope observation and FTIR analysis. The reduction of barrier properties was evaluated by electrochemical impedance spectroscopy. In case of red and black pigmented coatings, the degradation was related to the polymer matrix and the pigments. On the contrary, the white pigmented sample showed a lower degradation level only correlated to the matrix.