Research: Ion-Exchanged Anticorrosive Pigment in WB Epoxy Ester Coatings

As an eco-friendly rust-preventive pigment, SEI (Sodium Ester Ion) rust-proof pigment has attracted widespread attention . It uses silica as a carrier and undergoes surface modification (most commonly calcium ion modification), achieving genuine environmental friendliness, non-toxicity, and harmlessness. Meanwhile, ion-exchanged anticorrosive pigments demonstrate outstanding corrosion resistance, making them ideal for heavy metal protection. The most viable alternative to rust pigments operates through two mechanisms: (1) The porous silica carrier adsorbs corrosion ions to mitigate corrosion; (2) Calcium ions on the surface undergo ion exchange with corrosion ions, forming a calcium silicate passivation film at the coating base to protect the substrate .Waterborne epoxy ester coatings, as a type of waterborne anti-corrosion coatings, are widely used in fields such as steel structures and automotive parts.

This study delved deeply into the comparison of the anti-corrosion performance of SEI anti-rust pigments with zinc phosphate in different waterborne epoxy ester resin systems, the performance differences of anti-rust pigments from different manufacturers, the addition amounts, and the optimization of the defoaming system in the coating formula.

The basic formula of the coating is shown in Table .

(1) Slurry： Add water, resin, dispersant, defoamer, titanium dioxide, carbon black, barium sulfate and anti-rust pigment to the grinding tank in sequence according to the formula quantity, and stir at high speed at 1,500 r/min for 15 minutes. Then, zirconium beads are introduced for grinding until the fineness is ≤30 μm, and the material is discharged.

(2) Post-addition stage: Put waterborne epoxy ester resin into the mixing tank and add the above-mentioned slurry while stirring. Subsequently, pH regulators, leveling agents, defoamers, film-forming AIDS, sand bacteria agents, anti-flash rust agents and thickeners were added. The viscosity was adjusted to 80-90 KU (at 25 ℃), and then filtered through 120-mesh gauze to obtain waterborne epoxy ester coatings.

(3) Coating film

Base material treatment: Degreasing of cold-rolled steel plate, grinding with 120-mesh sandpaper, and cleaning with alcohol. Add 8% to 15% water to the waterborne epoxy ester coating, adjust the viscosity (apply 4 cups) for 25 to 35 seconds, and then spray it with an air gun. The dry film thickness should be controlled at 40 to 50 μm. Level for 15 minutes and bake at 80 ℃ for 30 minutes. Then, the sample was placed at room temperature for curing for 7 days before testing.

Conclusion

(1)   The salt spray resistance of ion-exchange anti-rust pigments in various epoxy ester resins is significantly better than that of zinc phosphate, indicating that they have strong versatility.

(2) Currently, there are numerous types of commercialized ion-exchange anti-rust pigments on the market, and their physical and chemical parameters are also inconsistent. Products with high calcium content and low pore volume have excellent anti-corrosion performance.

(3) The higher the addition amount of ion-exchange anti-rust pigments, the better the anti-corrosion performance of the coating. When the addition amount exceeds 7%, the performance improvement is slow. In addition, as the addition amount keeps increasing, the viscosity of the coating keeps rising, which will affect

The production and application of coatings are affected, and at the same time, the cost is constantly rising. Therefore, considering multiple factors comprehensively, it is recommended that the addition amount be controlled at 5% to 7%.

(4) Due to the porous structure of the silica carrier of ion-exchange anti-rust pigments, the coating system shows a bubble stabilization phenomenon. By optimizing the defoaming system and choosing the appropriate combination of concentrated liquid silicone defoamer and emulsion defoamer, a good application effect can be achieved.