Preparation And Performance Study Of Polymer-based Anti-corrosion And Scale-inhibiting Functional Coating

Circulating cooling water is used in a huge amount in industrial production,but with the extension of working time,inorganic salts and scales are inevitably deposited on the surface of water pipelines and water treatment equipment,which seriously reduces the heat and mass transfer efficiency of the equipment.It was reported that every 1 mm of scale deposited on the surface of heat transfer equipment will waste 8%of the coal.In today’s energy resources are so scarce,it is more important to delay the deposition of scale on the surface of the equipment.Adding high-efficiency inhibitor to circulating water is a commonly used anti-scaling method in the industry.However,this method greatly reduces the utilization rate of the scale inhibitor,and the discharged scale inhibitor may pollute the environment.Therefore,it is necessary to combine the scale inhibitor with the microcapsule technology to realize the scale inhibitor’s slow release and efficient utilization.In this study,three long-lasting anti-corrosion and scale-inhibiting coatings were prepared by designing three high-efficiency slow-release microcapsule fillers and adding high-efficiency slow-release fillers to organic resins.（1）Through a simple spray method,hydroxyethylidene diphosphonic acid（HEDP）was filled inside poly-α-cyanoacrylate microcapsules（PEC）,and a new type with excellent scale inhibition and sustained release effects was successfully prepared.Microencapsulated Sustained Release Filler（PEC&HEDP）.In addition,an appropriate amount of microcapsules was added to spray polyurea resin（SPUA）,and SPUA/PEC&HEDP_70&30 composite coatings were successfully prepared.Moreover,the barrier and corrosion resistance properties of the coatings were evaluated by electrochemical impedance spectroscopy（EIS）and salt spray corrosion tests.The results show that the barrier properties of the composite coatings are significantly higher than those of pure SPUA coatings.In addition,the scale inhibition performance of the composite coating was tested in supersaturated Ca CO₃ solution.The results show that the scale inhibition efficiency of the composite coating with 20%slow-release microcapsule filler is as high as 80.5%.（2）Water-based coatings have attracted much attention due to their significant advantages such as high safety,low pollution,and room temperature curing.However,the industrial application of waterborne epoxy is limited due to the poor barrier properties and mechanical durability.In order to further improve the sustained-release stability of the microcapsules and reduce the environmental pollution caused by the organic solvents used in traditional coatings.In this study,the porous slow-release microcapsule filler was improved.HEDP was used as scale inhibitory active substance,Si O₂ was used as carrier,combined with phospholipid membrane with selective permeation function,and functional slow-release nanofiller（LT/Si O₂/HEDP）.The barrier effect of water-based coatings was successfully improved by adding functional slow-release nano-fillers.Simultaneously,the coatings had excellent scale inhibition properties.The impedance modulus of the composite coating with slow-release fillers was increased by about 1 order of magnitude,and the scale inhibition efficiency was as high as80.7%.（3）It is well known that CO₃^2-and OH^-anions are difficult to exist in an acidic environment,while Ca CO₃ and Mg（OH）₂ are easily formed and deposited on the device surface under alkaline conditions.Therefore,it is necessary to design a smart microcapsules and coatings that remain inert under neutral and acidic conditions and rapidly release scale-inhibiting active substances under alkaline conditions.In this study,the porous polysulfone microcapsules were prepared by the mixed solvent evaporation method.The microcapsules were used as the carrier,HEDP as the active substance for scale and corrosion inhibition,and stearic acid（SA）as the coating.The p H-responsive smart microcapsule slow-release filler was successfully prepared.Then,smart microcapsules were added to polyurea resin to prepare p H-responsive smart composite coatings with anticorrosion and scale inhibition properties.The results show that SA/PSF/HEDP microcapsules have p H-triggered activity in an alkaline environment.The composite coating exhibits excellent scale inhibition performance in alkaline supersaturated Ca CO₃ solution.This was attributed to the fact that the HEDP in the microcapsules was released to the coating surface and complexed with Ca²⁺in the solution,which finally delayed the deposition of scale on the coating surface,and the scale inhibition efficiency was as high as78.57%.Meanwhile,the SP/SA/PSF/HEDP composite coating has good corrosion resistance proved by local electrochemical impedance spectroscopy（EIS）.