Because flammable organic solvents are emitted during the construction process, oil-based conductive coatings generally result in potential safety problems. A high content of conductive mediums can also weaken the adhesive and protective abilities of existing conductive coatings. Therefore, an anticorrosive and conductive coating was prepared on Q235 steel substrate by spraying the multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) dispersion with a low MWCNT content in this work. The effect of the MWCNT content on the electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating was investigated. It was concluded that a spatial network structure of MWCNTs-WPU was formed to make the coating structure more compact. The electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating first increased and then decreased as the MWCNT content increased. When the MWCNT content was only 0.2 wt % (which was far lower than that of the existing conductive coatings at 1 wt %), the coating began to conduct electricity; its resistivity was 12,675.0 Ω·m. The best combination property was the 0.3 wt % MWCNTs/WPU conductive coating. Its adhesive strength was 19.99% higher than that of pure WPU coating. Its corrosion rate was about one order of magnitude lower than that of pure WPU coating after being immersed in 3.5 wt % NaCl solution for 17 days.

Electrostatic spraying (ES) was used to prepare multi-walled carbon nanotube (MWCNT)/waterborne polyurethane (WPU) abrasion-proof, conductive coatings to improve the electrical conductivity and mechanical properties of WPU coatings. The dispersity of MWCNTs and the electrical conductivity, surface hardness, and wear resistance of the coating prepared by ES (ESC) were investigated. The ESC was further compared with coatings prepared by brushing (BrC). The results provide a theoretical basis for the preparation and application of conductive WPU coatings with excellent wear resistance. The dispersity of MWCNTs and the surface hardness and wear resistance of ESC were obviously better than those of BrC. With an increase in the MWCNT content, the surface hardness of both ESC and BrC went up. As the MWCNT content increased, the wear resistance of ESC first increased and then decreased, while the wear resistance of BrC decreased. It was evident that ESC with 0.3 wt% MWCNT was fully capable of conducting electricity, but BrC with 0.3 wt% MWCNT failed to conduct electricity. The best wear resistance was achieved for ESC with 0.3 wt% MWCNT. Its wear rate (1.18 × 10⁻¹⁰ cm³/mm N) and friction coefficient (0.28) were the lowest, which were 50.21% and 20.00% lower, respectively, than those of pure WPU ESC.

Due to the presence of many flammable substances in the working environments of the petrochemical industry, anticorrosive conductive coatings need to be used on metal equipment to avoid safety accidents like fires. However, existing conductive solvent-based coatings are volatile when exposed to flammable and toxic organic solvents. Thus, in this work, a series of eco-friendly anticorrosive waterborne polyurethane (WPU) composites with multi-walled carbon nanotubes (MWCNTs) were prepared via a low-cost and practical process; the dispersion of MWCNTs was revealed when present in different amounts, and the mechanism behind the conduction of WPU composites was determined. We concluded that low amounts of MWCNTs were well dispersed, generating a conductive network, and the WPU composite was not entirely covered by the MWCNT particles, so the electrical conductivity in certain parts of the coating was good. When the content of MWCNTs was excessive, some stretched MWCNTs dispersed to the top of the composite and many MWCNTs agglomerated at the bottom. Additionally, when the content of MWCNTs was increased, the electrical conductivity, corrosion resistance, and adhesion strength of the WPU composite decreased. Our results could provide a theoretical foundation for the preparation of anticorrosive conductive waterborne composites for protecting equipment in the petrochemical industry.

Waterborne polyurethane (WPU) coatings hold advantages of good toughness, low cost and environmental protection. However, the low water contact angle (WCA), poor wear and corrosion resistance make them unsuitable for application in the superhydrophobic coatings such as antipollution flashover coatings for transmission lines, self-cleaning coatings for outdoor equipment and waterproof textiles. A series of superhydrophobic WPU composites (SHWPUCs) with micro-rough surface structure was prepared by electrostatic spraying nano-SiO₂ particles on WPU composites with low surface energy. It showed that as the hydrophobic system content rose the WCAs of the composites first increased and then remained stationary; however, the adhesion and corrosion resistance first increased and then decreased. An appropriate addition of the hydrophobic system content would lead to a dense coating structure, but an excessive addition could increase the interfaces in the coating and then reduce the coating performance. When the mass ratio of the WPU dispersion, polytetrafluoroethylene (PTFE) particles and modified polydimethylsiloxane was 8:0.3:0.4, 10 g/m² nano-SiO₂ particles were sprayed on the uncured coating surface to construct the SHWPUC with a WCA of 156°. Compared with pure WPU coating, its adhesion and corrosion resistance increased by 12.5% and one order of magnitude, respectively; its wear rate decreased by 88.8%.

The addition of abundant fillers to obtain conductive and superhydrophobic waterborne polyurethane (WPU) composites generally results in increased interfaces in the composites, leading to reduced adhesion and poor corrosion resistance. Fillers such as Polytetrafluoroethylene (PTFE) and multi-walled carbon nanotubes (MWCNTs) were first treated by a coupling agent to reduce the contents of the fillers. Thus, in this work, WPU superhydrophobic conductive composites were prepared using electrostatic spraying (EsS). The polar groups (-OH and -COOH, etc.) on the WPU, PTFE, and MWCNTs were reacted with the coupling agent, making the WPU, PTFE, and MWCNTs become crosslinked together. Thus, the uniformity of the coating was improved and its curing interfaces were reduced, causing enhanced corrosion resistance. The dehydration reaction that occurred between the silane coupling agent and the polar surface of Fe formed -NH₂ groups, increasing the adhesion of the coating to the steel substrate and then solving the problems of low adhesion, easy delamination, and exfoliation. With the increased content of the modified fillers, the conductivity and hydrophobic property of the composite were amplified, and its corrosion resistance and adhesion were first strengthened and then declined. The composite with the WPU, PTFE, MWCNTs, and KH-550 at a mass ratio of 7:1.5:0.1:0.032 held excellent properties; its volume resistivity and WCA were 1.5 × 10⁴ Ω·cm and 155°, respectively. Compared with the pure WPU coating, its adhesive and anticorrosive properties were both better. This provides a foundation for the fabrication and application of anticorrosive and conductive waterborne composites.