Influence of different colour pigments on the properties of powder deposited organic coatings

• Pigments are used inside paints for aesthetical and functional reason.
• The colour pigment/matrix ratio affects the aesthetical and functional properties.
• Increasing the colour pigment/matrix ratio the aesthetical properties increases.
• Increasing the colour pigment/matrix ratio the functional properties don not change.

An organic coating is made of many different constituents to obtain both good protection of the substrate and appearance properties. Among the different constituents, pigments, additives and fillers are the most important. Usually, pigments are added both for corrosion protection purposes and for enhancing the aesthetical properties. However the pigments added to the polymeric matrix for aesthetical purposes could not influence only the appearance of the material. In fact they could also affect its corrosion protection properties. This paper investigates the effect of three different colour pigments (grey, red, orange) and three different concentrations of colour pigment (standard, standard + 25 wt%, standard + 50 wt%) on both appearance and corrosion protection properties of powder deposited coatings.For this purpose, polyester powder coating applied on aluminium substrate were studied. The effect of UV-B lamps ageing and cyclic UV-B cabinet and acetic acid salt spray chamber exposure was investigated. Considering appearance properties, gloss and colour measurements were carried out. As far as corrosion protection properties are concerned, electrochemical impedance spectroscopy measurements were performed. The different pigment/matrix ratios were proved to noticeably influence the gloss and colour stability during the ageing (in particular considering the orange and red samples) and to slightly affect the barrier properties of the coatings.