Abstract
A thicker layer of multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) anticorrosive and conductive coating was respectively prepared on the Q235 steel substrate by brushing (Br) and electrostatic spraying (ES) in this work. The effect of coating process on the dispersion of the MWCNTs and the electrical conductivity, corrosion resistance, and bond strength of the coating was investigated. It was shown that the coating prepared by ES (ES coating) had a smooth surface, few defects and evenly dispersed MWCNTs. The coating prepared by Br (Br coating) had a rough surface, some defects and obviously agglomerated MWCNTs. The electrical conductivity, corrosion resistance, and bond strength of the ES coating were higher than those of the Br coating with the same MWCNT content. As the MWCNT content increased, the electrical conductivity of the ES coating increased, however, its corrosion resistance and bond strength first increased and then decreased. The resistivity of ES 0.3 wt% MWCNTs/WPU coating (12808.4 Ω·m) met the standard requirement of the conductive coating. Its corrosion rate was 3.50×10-5 mm/a immersed in 3.5 wt% NaCl solution. Its bond strength to the Q235 steel substrate was higher than that of ES pure WPU coating. As the MWCNT content increased, the electrical conductivity of the Br coating increased, however, its corrosion resistance and bond strength decreased. When the MWCNT content was 0.6 wt%, the Br coating would conduct electricity. Its corrosion rate was 5.24×10-2 mm/a.
Highlights
Due to the characteristics of severe corrosivity, flammability and explosivity, petrochemical enterprises would be at risk of seriously safety problems such as fire hazards when triboelectrification occurs
That far more waterborne polyurethane (WPU) resins would be adhered to the surfaces of the multi-walled carbon nanotubes (MWCNTs) could enlarge the interface bonding performance between the MWCNT and the WPU, which would enhance the dispersion of the MWCNTs in the WPU resins
It may lead to the results that the good dispersibility of the MWCNTs was useful to produce the tunneling effect on the electrical conductivity, which could help the coating with relatively low MWCNT content to be capable to conduct electricity
Summary
Due to the characteristics of severe corrosivity, flammability and explosivity, petrochemical enterprises would be at risk of seriously safety problems such as fire hazards when triboelectrification occurs. In order to export the static electricity arising from triboelectrification which may cause flammable materials to be on fire, and to prevent metal equipment from corrosion, a layer of conductive and anticorrosive organic coating should be coated on the surface of metal equipment.. The additions of the CNTs to the water-based coatings would effectively improve the electrical conductivity, corrosion resistance, and mechanical capacity of the composites.. The multi-walled carbon nanotubes (MWCNTs) with different contents were respectively dispersed in the WPU24 by reasonable techniques of magnetic stirring and ultrasonic dispersion to obtain evenly dispersed MWCNTs/WPU emulsions, and a series of thicker layer of MWCNTs/WPU anticorrosive and conductive coatings were respectively prepared on the Q235 steel substrates by two coating processes of Br and ES.. The effect of coating process on the dispersion of the MWCNTs and the electrical conductivity, corrosion resistance, and bond strength of the coating was studied by comparison. The research results would provide a theoretical basis for dealing with problems of the surface protection of the equipment in petrochemical industry
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