Krzysztof Kowalczyk

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

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).

Synthesis and characterization of the aluminium phosphates modified with ammonium, calcium and molybdenum by hydrothermal method

Abstract Synthesis and characterization of the aluminum phosphates modified with ammonium, calcium and molybdenum were conducted. The influence of process parameters (reactive pressure and molar ratios) in the reaction mixture were studied. The contents of the individual components in the products were in the range of: 10.97–17.31 wt% Al, 2.65–13.32 wt% Ca, 0.70–3.11 wt% Mo, 4.36–8.38 wt% NH3, and 35.12–50.54 wt% P2O5. The materials obtained in the experiments were characterized by various physicochemical parameters. The absorption oil number was in the range from 67 to 89 of oil/100 g of product, the surface area was within the range of 4–76 m2/g, whereas the average particle size of products reached 282–370 nm. The Tafel tests revealed comparable anticorrosive properties of aluminum phosphates modified with ammonium, calcium, molybdenum in comparison with commercial phosphate.