MECHANOCHEMICALLY MODIFIED NATURAL SILICATE AS AN INHIBITING PIGMENT FOR PROTECTING ALUMINUM ALLOYS FROM CORROSION
DOI:
https://doi.org/10.15407/dopovidi2026.04.080Keywords:
wollastonite, zinc monophosphate, aluminum alloy, corrosion, anticorrosive pigment, electrochemical impedance spectroscopyAbstract
A composite anticorrosive pigment was synthesized by mechanochemical modification of wollastonite with zinc monophosphate. X-ray diffraction analysis showed the disappearance of zinc monophosphate crystal peaks after treatment, indicating the formation of an amorphous or nanocrystalline phosphate phase on the surface of the wollastonite particles. This transformation is expected to enhance both the pigment’s reactivity and its corrosion- inhibitingperformance. Thecorrosionprotectionprovidedby aqueous extracts ofwollastonite, zinc monophosphate, their physical mixture, and the mechanochemically modified composite pigment was evaluated for D16T aluminum alloy in a 0.1 wt.% NaCl solution using electrochemical impedance spectroscopy. The composite pigment exhibited significantly higher protective efficacy than any of its individual components or a simple physical mixture of them. In particular, the impedance modulus at a frequency of 0.01 Hz increased approximately fifteenfold compared to a chloride solution without an inhibitor and approximately fivefold compared to a solution containing a physical mixture of wollastonite and zinc monophosphate. Equivalent circuit analysis revealed a significant increase in both charge transfer resistance and surface film resistance, accompanied by a decrease in double-layer capacitance, indicating the formation of an effective protective barrier on the alloy’s surface. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy confirmed the formation of a homogeneous protective layer enriched with calcium, zinc, aluminum, and phosphorus. The enhanced protective performance of the composite pigment is due to the increased solubility and reactivity of the amorphous phosphate compounds formed during mechanochemical treatment, as well as their synergistic interaction with the silicate components. These results indicate that the composite pigment based on wollastonite and zinc monophosphate is a promising and environmentally safe corrosion inhibitor for organic coatings on aluminum alloys.
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