Abstract:

Conducting polyaniline(ES) was prepared using acidic phosphate(HPAA) as dopant of emeraldine base(EB), which can be dispersed in nanoscale in the polyurethane or polyurethane acrylates based matrix, subsequently, ultraviolet-thermal double cured polyaniline anti-corrosion coating without any heavy metals was prepared. The anti-corrosion layer was obtained by ultraviolet light curing in 3~5 s and subsequent thermal curing at 80 ℃ in 1~3 min. Particle size of ES increases with increasing mass fraction of ES in the coating matrix, meanwhile, the aggregation of ES molecules is enhanced. This is because ES is not miscible in polyurethane or polyurethane acrylates in the coating system. The particle size of ES can be controlled between 80 nm and 750 nm, it is ca. 80~119 nm when the mass fraction of the ES in the coating is 1.0%, and is increased to 500~750 nm when mass fraction of ES is 5.0%. The increase of particle size of ES is accompanied by the increase of porosity of anti-corrosion coating, leading to poorer anti-corrosion performance. The absolute impedance at 0.1 Hz(|Z|_{0.1 Hz}) of 1.0 % ES anti-corrosion coating protected mild steel can maintain 1.0×10⁸ Ω·cm² after 2160 h immersion in 3.5% NaCl solution, while that from UV curing coating protected mild steel is 1.0×10⁷ Ω·cm²,indicating better anti-corrosion performance of this double cured coating. The double cured anti-corrosion coating does not show any red rust and blister after 500 h cross scratch neutral salt spray test, while the rust is observed in the UV-cured anti-corrosion coating, though the rusted frontier around the scratch is still less than 1 mm.

Key words: polyaniline, ultraviolet-thermal double curing, anti-corrosion coating