Influence of novel ammonium-modified zinc-free phosphate nanofillers on anticorrosive features of primer-less polyurethane top-coating compositions

Abstract

Anticorrosive polyurethane coating compositions were compounded using novel zinc-free nanosized phosphates: aluminum ammonium phosphates (AAP) or calcium aluminum ammonium phosphates (CAAP). For comparison, a nanosized strontium phosphate (SP), AAP/SP mixtures, and a microsized zinc phosphate (ZP) were tested. Paints containing ammonium-modified phosphates exhibited similar or a slightly higher viscosity than systems with SP or ZP. Nevertheless, coatings with the AAP or CAAP reached significantly better gloss and adhesion to a steel substrate as well as a slightly higher hardness. Results of a salt spray test showed that anticorrosive properties of the coatings containing AAP/SP mixtures were markedly better in relation to the systems containing solely AAP, CAAP, SP, or ZP. Electrochemical tests revealed the best barrier/anticorrosive features for AAP (electrochemical impedance spectroscopy and potentiodynamic polarization) or SP and CAAP (a novel electrochemical noise technique).

Strontium-based nanosized phosphates as anticorrosive fillers of epoxy and polyurethane coating compositions

“…electrochemical tests of the anticorrosive fi llers or accelerated tests of the coatings). Moreover, sizes of anticorrosive fi llers particles and their dissipation effi ciency in coating compositions should be considered as important parameters infl uencing properties of dry/ cured paints 9,10,11,12 . In this work, a Zn-free nanosized strontium phosphate (SP) and a strontium aluminum phosphate (SAP) were tested as anticorrosive fi llers in primer-less solvent-borne 2K coating compositions compounded using an epoxy or a polyurethane (i.e.…”