Study On Preparation And Performance Of Self-cleaning Anticorrosive Coatings

Scale formation and dew point corrosion in flue gas heat exchanger not only make it difficult to operate for a long time,but also cause enormous economic costs.Due to the lack of superamphiphobicity,traditional coatings are easily penetrated by corrosive ions and lose protection.In recent years,superamphiphobic composite coatings with special wettability have received considerable attention in anticorrosion.Based on the theory of wettability and the biomimetic principle,polytetrafluoroethylene(PTFE)emulsion and epoxy resin were regarded as film former.The low thermal conductivity and high thermal conductivity fillers were introduced to construct micro/nanostructure,respectively.The low surface energy substance was added to improve the superamphiphobicity.It is believed that fabrication of excellent mechanical properties and anticorrosive superamphiphobic coatings by simple spraying will provide the possibility of service in the working environment of flue gas heat exchanger.The main research results are as follows:(1)The dispersion problem of hydrophobic substances was solved by introducing modified silica dispersion into PTFE emulsion.At the same time,modified aluminum tripolyphosphate(Modified ATP)with corrosion resistance was introduced to fabricate PTFE/ATP/SiO2 superamphiphobic composite coatings.Zeta potential instrument results indicated that pH,silica concentration,modified silica concentration and particle size had certain effect on the stability of coating.The coating with 36 wt%modified silica(462.25±4.65 nm)achieved superamphiphobicity,with contact angles of 158±0.7°,151±10.6°toward water and ethylene glycol,respectively.In addition,contact angles of acid-base solutions(pH=1-14)were higher than 150°.It had excellent impact resistance,strong adhesion and high temperature resistance(Superamphiphobicity within the range of 425℃).Electrochemical tests showed that the coating had long-term protection efficiency.(2)Sodium silicate and curing agent(Modified ATP)were introduced into PTFE emulsion with hydrophobic silica to enhance the hardness and wear resistance of the coating.Multifunctional superamphiphobic coatings were prepared on the surface of tinplate by a simple spray method.The coating with 35.53 wt%hydrophobic silica(360 nm)possessed superamphiphobic property,with high contact angles of 160±0.7° and 156±0.9° toward water and glycerol,respectively.The coating can withstand a high temperature of 415 ℃,with strong adhesion and hardness of 6H.After 140 cycles of abrasion,it still had superhydrophobicity.The coating exhibited excellent antifouling and self-cleaning properties for slurry(45 wt%)and silica(100 nm).With the increase of low thermal conductivity fillers,the thermal conductivity of coating can be reduced to 0.012 W/(m·K).Finite element method was used to explain the insulation mechanism of coating.The infrared thermography was used to observe slowing down heat transfer process and prove the correctness of the model.It was worth noting that the coating still exhibited superhydrophobic performance to repel acid-base solutions after 120 h acid and alkali immersion.(3)Superamphiphobic/anticorrosive composite coatings with hierarchical micro/nanostructure successfully fabricated by integrating PTFE particles,hydrophobically modified Al2O3 and flake graphite into epoxy resin.The superamphiphobic surfaces with high contact angles toward water(163.3±0.6°),glycerol(158.4±0.9°),ethylene glycol(153.1±1.1°),phenol(130.4±0.3°)and solutions with pH=1-14(>150°).The composite coating possessed strong adhesion,high thermal conductivity(1.805 W/(m·K))and excellent wear resistance.It still had superhydrophobic properties after 1000 cycles of abrasion or 150 times of finger wear,tape adhesion and knife scraping.After immersion in 1 mol/L HCl,1 mol/L KOH and 3.5 wt%NaCl solutions for 30 d,the water contact angles of coating were 138±1.3°,140±1.1° and 140±0.7°,respectively.The electrochemical results showed that the composite coating improved anticorrosive performance with lower corrosion rate(30 μm/year)and higher protection efficiency(99.25%)after soaking in 3.5 wt%NaCl for 30 d.