The combined role of inhibitive pigment and organo-modified silica particles on powder coatings: Mechanical and electrochemical investigation

• Organo-modified silica particles (OSP) and anticorrosive pigments (ZMP) were added to powder coatings.
• Two opposite effects of addition OSP to coatings containing ZMP were detected.
• OSP incorporation needs to be in low percentages to achieve a synergistic effect between the two additives.
• The optimal combined system was established for 1.0 wt% of OSP.

The addition of organo-modified silica particles (OSP) to powder coating containing zinc molybdenum phosphate pigment (ZMP) has been investigated. The OSP were directly incorporated at different concentrations (1, 2.5, 3.5 and 4.5 wt%) in a polyester powder monolayer coating with 10 wt% ZMP. The adhesion and anticorrosion properties were evaluated by means of adhesion studies and different electrochemical techniques: electrochemical impedance spectroscopy (EIS) and an accelerated cyclic electrochemical technique (ACET). The optimum quantity of OSP that gave maximum anticorrosive performance of the coating system was determined (1.0%), however two opposite effects of addition on the coatings led to a reduction of anticorrosive properties for higher contents. Finally, the electrochemical behaviour of the optimized combined system was compared to the effects achieved when both additives were separately added to powder coatings by means of an additional electrochemical test.