Functional Coating Preparation And Performance Study Of Main Cooling Rollers For Power Cell Diaphragm Equipment

Power battery diaphragm equipment is an important equipment for the production of new energy battery diaphragm at present.The battery diaphragm produced by it has uniform thickness,smooth surface,no bubbles and good performance.The main cold roll is the main cooling component in the power battery diaphragm equipment,and the battery film can be formed after the rapid cooling of the main cold roll.However,in the working environment where circulating cooling water is supplied for a long time,a large amount of scale will be generated on the inner surface of the main cold roll.The existence of a large amount of scale will not only cause severe corrosion problems on the inner surface of the main cold roll,but also reduce the cooling efficiency of the inner surface of the main cold roll,thus affecting the quality of the battery diaphragm.Further to industrial production caused a significant waste of energy and economic losses.Therefore,it is very important for the future industrial production to solve the corrosion and scale resistance of the inner surface of the main cold roll.Polytetrafluoroethylene(PTFE)has a strong chemical stability,it has a low surface free energy,has good non-adhesion and hydrophobic.Therefore,PTFE can be used as an excellent anti-fouling material to modify metal surface.In this paper,based on the working condition of the inner surface of the main cold roll of the power battery diaphragm equipment,based on the theory of three Ni-Cu-P composite coating system explored by many researchers,the surface of the Q235B low carbon steel commonly used in the main cold roll through chemical composite plating technology,by using the single factor variable method,change the concentration of PTFE in the plating solution,Ni-Cu-P-PTFE composite coatings with PTFE concentrations of 10 m L/L,15 m L/L and 20 m L/L were deposited on the surface of Q235B mild steel,and a series of studies on Ni-Cu-P-PTFE composite coatings were carried out.The main research contents and conclusions of this paper are as follows:(1)Based on the theory of ternary Ni-Cu-P alloy composite coating,the single-factor variable method was used to change the PTFE concentration in the plating solution.The Ni-Cu-P-PTFE composite coating with PTFE concentration of 10 m L/L,15m L/L,20 m L/L was plated on the surface of Q235B mild steel by chemical composite plating method.The effects of different PTFE concentrations on the phase composition,surface morphology and element distribution of Ni-Cu-P-PTFE composite coatings were investigated by XRD,SEM and EDS.The results show that different PTFE concentrations have no significant effect on the phase structure,cross section morphology and element distribution of Ni-Cu-P-PTFE composite coatings.The Ni-Cu-P-PTFE composite coatings with three different PTFE concentrations have amorphous structure and can be tightly adsorbed and deposited on the substrate surface.The average thickness is about 15μm,and the elements are uniformly distributed on the surface of the coating.(2)The surface roughness,Vickers hardness and bonding strength of Ni-Cu-P-PTFE composite coatings were measured by portable roughness tester,EM-1500L micro-Vickers hardness machine and GP-TS2000M/50KN universal material testing machine.The effects of different PTFE concentrations on surface roughness,Vickers hardness and bonding strength of Ni-Cu-P-PTFE composite coatings were analyzed.The results showed that the surface roughness,microhardness and bonding strength of Ni-Cu-P-PTFE composite coatings were affected by different PTFE concentrations.In three Ni-Cu-P-PTFE composite coatings with different PTFE concentrations,The surface of Ni-Cu-P-PTFE composite coating with PTFE concentration of 20 m L/L is the smoothest,and its surface roughness is 1.18.The microhardness and bonding strength of Ni-Cu-P-PTFE composite coatings with PTFE concentration of 10 m L/L are the highest,and the values are 674 HV and 26 N/mm~2,respectively(3)The corrosion tests of Ni-Cu-P-PTFE composite coatings were carried out in15 wt%Na Cl and 5 wt%HCl respectively for seven days.The corrosion resistance of Ni-Cu-P-PTFE composite coatings was investigated by AC impedance method and polarization curve method.By analyzing the corrosion results,the corrosion resistance of Ni-Cu-P-PTFE composite coatings with different PTFE concentrations was evaluated.The effect of PTFE content on the corrosion resistance of Ni-Cu-P-PTFE composite coatings was investigated.The results show that Ni-Cu-P-PTFE composite coating on Q235B mild steel can obviously improve the corrosion resistance of Q235B mild steel.Among the three kinds of Ni-Cu-P-PTFE composite coatings with different PTFE concentrations,the corrosion resistance is the best Ni-Cu-P-PTFE composite coatings with PTFE concentration of 10 m L/L.The corrosion resistance of Ni-Cu-P-PTFE composite coatings decreases with the increase of PTFE concentration in the plating solution.(4)Ni-Cu-P-PTFE composite coatings were tested in 60 ~oC saturated calcium carbonate solution for 15 days.Based on the analysis of scaling test results,the anti-scaling performance of Ni-Cu-P-PTFE composite coatings with different PTFE concentrations was evaluated.The effects of contact Angle and surface free energy on the anti-scale properties of Ni-Cu-P-PTFE composite coatings were investigated,and the anti-scale mechanism of Ni-Cu-P-PTFE composite coatings was revealed.The results show that Ni-Cu-P-PTFE composite coating on the surface of Q235B mild steel can obviously improve the anti-scaling property of Q235B mild steel.The larger the static contact Angle is,the lower the surface free energy is.The lower the free energy of solid surface,the better its anti-scaling performance.The static water contact Angle and surface free energy of Q235B low carbon steel and Ni-Cu-P-PTFE composite coatings with three different PTFE concentrations are 93.8~o,120.4~o,150.3~o,135.4~o,37.6 m J/m~2,2.56 m J/m~2,0.96 m J/m~2,1.98 m J/m~2,respectively.Therefore,among the three different Ni-Cu-P-PTFE composite coatings with PTFE concentration of 15 m L/L,the scaling resistance of Ni-Cu-P-PTFE composite coatings is the best.