Preparation Of Anti-corrosion Coating On The Surface Of Water Ring Pump Disc In Marine Environment And Serviceability Study

Water-ring vacuum pump is widely used in marine industry.As a key part of the water ring vacuum pump,the disc is easily corroded due to its material,working environment and cavitation,which shortens the service life of the equipment and increases the maintenance cost,thus affecting the popularization and application of the water ring vacuum pump in the marine equipment industry.Therefore,it is of great significance to improve the corrosion resistance of water ring vacuum pump disc.Organic coating is widely used in anti-corrosion treatment of metal due to its strong shielding effect and low material cost,among which epoxy coating is widely used.However,under the severe marine environment,the weather resistance,mechanical property and anti-corrosion performance of epoxy coating become worse,so it is urgent to improve and optimize the comprehensive performance of epoxy coating.Taking the water ring pump disc as the research object,this paper designed the sand blasting pretreatment process,optimized the ratio and content of PANI/Nd₂O₃ composite material and the type and content of epoxy resin curing agent,so as to improve the comprehensive performance of epoxy coating,and applied it to the disc surface to improve its reliability in marine environment.The research contents and conclusions of this paper are as follows:（1）Study on sandblasting pretreatment process of 304 stainless steel surface.The influence of sandblasting angle,time,distance and abrasive mesh on the surface morphology,roughness and the bonding strength of epoxy coating was analyzed,and the optimal sandblasting parameter combination was obtained through orthogonal test with the objective of improving the bonding strength of coating.The results show that the metal surface roughness（Ra）is 5-6μm,the bonding strength of the coating is higher,and the consistency of the surface morphology has a greater impact on the bonding strength.The order of influence of sandblasting process parameters on coating bonding strength is:abrasive mesh>sandblasting distance>sandblasting angle.The optimal sand blasting process parameter combination is:sand blasting angle 75°,sand blasting distance 10 cm,abrasive mesh 24,sand blasting time 60 s.Under this process,the bonding strength of epoxy coating can reach 20.2 MPa.（2）Preparation and Properties of PANI/Nd₂O₃ Modified Epoxy Coating.PANI/Nd₂O₃modified epoxy coating was prepared by taking epoxy resin as film-forming material and PANI/Nd₂O₃ composite material prepared by in-situ polymerization as filler.The influence of the ratio and content of PANI/Nd₂O₃ composite material on the anti-corrosion performance and service performance of epoxy coating was analyzed.The results show that the agglomeration of PANI is significantly improved by the addition of nano Nd₂O₃.The electrochemical test results show that 4%-PANI/Nd₂O₃-3/EP coating has the maximum low-frequency impedance value of 1.25×10⁹Ω·cm² and the minimum corrosion current density of 3.54×10^-11 A·cm^-2,showing the best corrosion resistance.The bonding strength reaches18.8 MPa,the hardness of pencil reaches 2H and the contact angle reaches 78.3°.The coating material remains in normal service state after 60 days of immersion in 3.5%Na Cl solution,and the comprehensive performance is ideal.（3）The effects of curing agents Polyamide 650,T-31 and 593 on the properties of PANI/Nd₂O₃-modified epoxy coatings were investigated.The results show that among the three kinds of curing agent,the bonding strength of the coating cured by T-31 is the highest,and the bonding strength of the coating cured by 25%-T-31 is up to 21.5 MPa.Polyamide650 cures the toughest coating,with 60%-650 coating pencil hardness of 3 H.The 593 cured coating has high corrosion resistance,with 26%-593 coatings having a maximum low-frequency impedance value of 1.08×10¹⁰Ω·cm² and a minimum corrosion current density of 1.49×10^-12 A·cm^-2.The contents of the three curing agents have little influence on the contact angle.The contact angle values of the cured coatings of T-31 and polyamide 650 are all about 80°,and the cured coating of 593 has the maximum contact angle,among which the contact angle of 26%-593 is 105.4°.The scratch immersion test shows that the 35%-T-31 coating has failed after 30 days of immersion,and the coating added with high content of593 and polyamide 650 curing agent shows excellent corrosion resistance,durability and service performance.（4）Study on Surface Coating Technology and Corrosion Resistance of Disc of Water Ring Vacuum Pump.The process flow of disc surface coating was designed,and the anti-corrosion coating was uniformly applied on the disc surface by the manual method of wire rod applicator and wool brush,and the corrosion resistance experiment was carried out.The results show that the solidified coating has high quality,uniform thickness and no shrinkage cavity.Through cost accounting,it was found that the coating cost of a single disc decreased by 39.15%compared to the existing coating cost of the manufacturer.