Anticorrosive 2K polyurethane paints based on nano- and microphosphates with high dispersing additive content

• Nanosized Al phosphate and microsized Al-Zn phosphate as anticorrosive fillers in paints.
• Nanosized Al phosphate improves hardness and adhesion of coats (PVC = 18.3) to steel substrates.
• Nanosized Al phosphate exhibits better protective properties than microsized Al-Zn phosphate.

Two-component solvent-borne polyurethane paints containing mica, quartz, TiO2, wollastonite, talc as well as either nanosized aluminum phosphate or microsized aluminum-zinc phosphate as anticorrosive filler have been tested. Three paints with various PVC and CPVC values had been prepared and applied onto steel substrate and cured at room temperature. An influence of commercial dispersing additive dose as well as a type and content of phosphate filler on features of tested paints and coatings has been investigated. However, the incorporation of nanosized aluminum phosphate into coating compositions increases their viscosity the cured paints exhibit higher adhesion to a steel substrates in comparison with coats based on microsized aluminum-zinc phosphate (both samples characterized with the same PVC value). Moreover, higher dose of dispersing additive causes higher value of the former parameter and either improves (in case of coats with nanofiller) or reduces adhesion (coats with microfiller). The results of corrosion tests in a salts spray chamber showed that paint system containing 9.8 wt.% of nanosized aluminum phosphate and 7.5 wt. parts of dispersing additive (per 100 wt. parts of all fillers/pigment content in coating compositions) had better protective properties than polyurethane coats containing 12.2 or 15.6 wt.% of commercial microsized aluminum-zinc phosphate and various auxiliary dispersing additive content.