An organic coating is made of different constituents to obtain good protection properties and aesthetical aspect. The research in this field is usually split in two ways. The first aim to study the corrosion protection properties and for this goal it considers the anticorrosive pigments. The second one aims at investigating the changes in the gloss and colours due to ageing and weathering by considering the effects of the presence of different coloured and optical effected pigments in the polymeric matrix. It is not usual to consider in the study of corrosion protection by means of organic coatings these last aspects. In several cases it could be not the correct approach. In fact the pigments added to the polymeric matrix for aesthetical purposes could not influence only the appearance of the material but they could also affect its corrosion protection properties. As a function of the desired colours, the convenient pigment/matrix ratio can dramatically change and the addition of additives could be needed to produce a layer with selected aesthetical and protection properties. This work represents an attempt to elaborate an integrated approach to consider the effects of the chromatic pigments on both the corrosion and appearance properties. For this purpose epoxy-polyester powder coating applied on aluminium substrate (without any further pre-treatment) were studied. In particular three different colours (red, orange and grey) were chosen in order to investigate the effect of three different sort of chromatic pigments. In addition, three different pigment/ matrix ratios were studied in order to analyse at the same time the effect of the pigment volume concentration on the appearance of the organic coating and its corrosion protection properties Therefore the effect of the different pigment/matrix ratios on the corrosion protection properties of the organic coatings were investigated by means of electrochemical impedance spectroscopy (EIS). In particular the influence of the different pigment/matrix ratios on the dielectric properties of the organic coatings and on the water uptake with immersion time in a conductive solution were investigated. On the other hand the ageing effects of accelerated laboratory test (such as UV lamps exposure) on the appearance properties of the different samples were evaluated through gloss and colour change measurements. The effect of the different pigment/matrix ratios on the corrosion protection properties and on the appearance properties of the organic coatings were described and correlated.
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