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Effect of curing process on properties of non-oriented environmentally friendly silicon steel insulating coating

  • Time of issue:2018-10-16 18:44

(Summary description)The curing process is the key process for silicon steel coating. This article prepares an environmentally friendly silicon steel insulation coating solution, and uses different curing process conditions to treat the non-oriented silicon steel insulation coating. By observing the difference in surface morphology, neutral salt spray test corrosion area, The insulation resistance value and the quality of electrochemical parameters are used to evaluate the surface state, corrosion resistance, electrochemical performance, insulation performance, etc. of the coating, and then to evaluate the quality of the coating curing process, which is useful for the actual production of silicon steel coatings. The application is instructive.

Effect of curing process on properties of non-oriented environmentally friendly silicon steel insulating coating

(Summary description)The curing process is the key process for silicon steel coating. This article prepares an environmentally friendly silicon steel insulation coating solution, and uses different curing process conditions to treat the non-oriented silicon steel insulation coating. By observing the difference in surface morphology, neutral salt spray test corrosion area, The insulation resistance value and the quality of electrochemical parameters are used to evaluate the surface state, corrosion resistance, electrochemical performance, insulation performance, etc. of the coating, and then to evaluate the quality of the coating curing process, which is useful for the actual production of silicon steel coatings. The application is instructive.

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  • Time of issue:2018-10-16 18:44
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  The curing process is the key process for silicon steel coating. This article prepares an environmentally friendly silicon steel insulation coating solution, and uses different curing process conditions to treat the non-oriented silicon steel insulation coating. By observing the difference in surface morphology, neutral salt spray test corrosion area, The insulation resistance value and the quality of electrochemical parameters are used to evaluate the surface state, corrosion resistance, electrochemical performance, insulation performance, etc. of the coating, and then to evaluate the quality of the coating curing process, which is useful for the actual production of silicon steel coatings. The application is instructive.

  With the increasing demand for electrical steel in my country, electrical steel production technology has gradually improved. Non-oriented silicon steel occupies a huge market share in the production of silicon steel in my country, and silicon steel coating is an indispensable key technology in the production of silicon steel products, which will definitely affect the production and development of silicon steel products, and with the development and growth of my country's silicon steel industry, Silicon steel coating has huge market potential. The curing process is the key process of silicon steel coating. This article prepares an environmentally friendly silicon steel insulating coating solution, and uses different curing process conditions to treat the non-oriented silicon steel insulating coating. By observing the difference in surface morphology, neutral salt spray test corrosion area, The insulation resistance value and the quality of electrochemical parameters are used to evaluate the surface state, corrosion resistance, electrochemical performance, insulation performance, etc. of the coating, and then to evaluate the quality of the coating curing process, which is useful for the actual production of silicon steel coatings. The application is instructive.

 
  SHAPE\*MERGEFORMAT
  1.1 Preparation of the coating
  Use anilox rollers to coat the phosphate-based non-oriented environmentally friendly silicon steel insulating coating solution prepared in the laboratory on the treated silicon steel substrate to ensure that the coating amount is between 1-1.5g/cm2, and the temperature is respectively selected as 300, 350, 400, 450 ℃ , The time is 10, 20, 30s to sinter and cure the coating to obtain the non-oriented environmentally friendly silicon steel insulating coating under different process conditions, and perform performance testing and characterization.
 
  1.2Test characterization
  Use the Shanghai Chenhua CHI660E electrochemical workstation to test the polarization curve and AC impedance of the coating. The traditional three-electrode system is used, the working area is 1cm2, the corrosive medium is 3.5% NaCl solution, the scanning rate is 5mV/s, and the AC impedance spectroscopy The scan frequency range is 10mHz-100kHz, and the scan rate is 0.05mV/s. Using the DCTC1200P neutral salt spray test chamber from Angelantoni, Italy, the corrosion resistance of the coating was tested according to GB/T10125-1997. According to GB/T2522-2007, use the HT-2007 type coating insulation resistance measuring instrument to test the insulation resistance of the coating to evaluate the insulation performance of the coating. Hitachi S-3400N scanning electron microscope was used to observe the surface micro morphology of the environmentally friendly silicon steel insulation coating after curing. Using the STA-449C thermal analyzer of German Netzsch company, under the protection of nitrogen, the heating rate is 10℃/min, and the non-oriented environmentally friendly silicon steel coating liquid is thermally analyzed. A Fourier transform infrared spectrometer from PerkinElmer, USA was used for infrared analysis of the coating.
 
  SHAPE\*MERGEFORMAT
  2.1Corrosion resistance

  The neutral salt spray test is used to evaluate the corrosion resistance of the coating. The percentage of rusted area after the 5h neutral salt spray test is shown in Figure 1.

  It can be obtained from Figure 1: In the neutral salt spray test, under the same curing time, with the increase of curing temperature (300-450℃), the corrosion resistance of the coating generally shows a gradually increasing trend. Among them, when the curing temperature is 300°C, the corrosion percentage of the coating under the three curing times is significantly higher than that under other process conditions, and the corrosion resistance of the coating is relatively poor, indicating that the coating is incompletely cured at this temperature. When the curing temperature is 350°C, with the increase of curing time, the corrosion percentage gradually decreases, indicating that with the increase of curing time (10-30s), the corrosion resistance of the coating is continuously improved. When the curing temperature is 400°C, the corrosion percentage of the coating under the three curing times is significantly lower than that under other process conditions, and the corrosion resistance is higher. The corrosion resistance is particularly excellent when the curing time is 20s and 30s. At 450°C, the corrosion percentages of 10s and 20s are low, but when the curing time reaches 30s, the corrosion percentage of the coating increases significantly, indicating that the corrosion resistance of the coating is poor at this time.

 
  2.2Insulation performance

  The insulation performance of the environmentally friendly silicon steel insulation coating is characterized by the measured insulation resistance value. The insulation resistance of the coating under different process conditions is shown in Figure 2.

  It can be seen from Figure 2 that different curing processes have different effects on the insulation performance of the coating. When the curing temperature is 300°C, the insulation resistance of the coating increases slightly with the increase of curing time. At 300℃, the highest value of insulation resistance is only 175Ωmm2. When the curing temperature reaches 350℃, with the increase of curing time, the insulation resistance of the coating obviously increases. After curing for 30s, the insulation resistance can reach more than 300Ωmm2. When the curing temperature is 400°C, the curing time of 20s and 30s has a significant increase in insulation resistance compared with the curing time of 10s, but the difference in resistance between the two is not much. But when the curing temperature is 450°C, it can be found that the insulation resistance value has a parabolic change trend with the increase of curing time, and the resistance value is lower than the resistance value at each curing time when the resistance value is lower than 400°C.

 
  2.3Surface topography

  In order to explore the micro morphology of the coating surface under different process conditions, combined with the neutral salt spray test and insulation performance test results, the silicon steel coating was selected at 300℃+10s, 350℃+30s, 400℃+20s, 450℃+ The four representative process conditions of 30s are shown in Figure 3. SHAPE\*MERGEFORMAT

  From Figure 3, the difference in the micro-morphology of the coating surface under the four process conditions can be clearly seen: when the curing process is 300℃+10s, the coating color is lighter and translucent, and the surface of the silicon steel substrate is uneven. , The coating is basically uncured; when the curing process is 350℃+20s, the color of the coating is obviously darkened, but the morphology of the substrate can also be found vaguely, and the degree of curing increases; when the curing process is 400℃+20s, the coating The surface is uniform and compact, with good coverage, and the coating has a good curing degree; when the curing process is 450℃+30s, the coating appears obvious defects, the surface is damaged by scorching, the silicon steel matrix is ​​exposed, and the lumps and powder morphologies are aggregated. , Indicating that the temperature is too high at this time, so that the coating is over-cured. The microscopic morphology of the coating under different processes can explain the relationship between the corrosion resistance of the coating and the insulation performance.

 
  2.4Electrochemical performance test
  2.4.1Tafel polarization curve

  Combining the experimental results of the neutral salt spray test and the insulation performance test, the Tafel polarization curves of the substrate and 4 process condition samples are selected, as shown in Figure 4, and the electrochemical parameters are listed in Table 1.

  From Figure 4 and Table 1, it can be seen that the corrosion current is basically the same under the four process conditions, which are of the same order of magnitude, and the corrosion potential is not much different, but when the curing temperature is 400℃, the curing time is 20s, and the polarization resistance is 30s. It is 2 times that under other conditions, indicating that the electrochemical parameters of the coating under this process condition are relatively excellent. At this time, the coating can effectively prevent the corrosion of chloride ions on the sample, and reduce the electron transfer rate between the anode and the cathode. Small, reducing the corrosion rate. Under different process conditions, the protection rate of the coating on the substrate is shown in Table 1. Under the four process conditions, the protection rate of the coating is greater than 98%, which can basically meet the protection of the coating on the substrate, which is consistent with the experimental results of the neutral salt spray test and the insulation resistance value. Among them, the corrosion protection rate of the coating at 400℃+20s is as high as 99.53%, indicating that the coating has the best protection effect on the substrate under this process condition.

 
  2.4.2AC impedance spectroscopy
  AC impedance spectra of the new environmentally friendly silicon steel insulating coating under different curing process conditions.
   It can be concluded from Figure 5 that the impedance arcs under the four process conditions are quite different. When the curing temperature is 400℃ and the curing time is 20s, the impedance arc radius of the coating is the largest, and it is significantly larger than the impedance of the other three process conditions. The radius of the arc.
   Table 2 lists the original circuit values of the fitted equivalent circuit, Rs is the solution resistance, RPo is the resistance in the coating hole, Rt is the coating corrosion reaction polarization resistance, Cc is the coating capacitance, and Cdl is the electric double layer capacitance. The larger the Rt value, the C. The smaller the value, the better the protective effect of the coating. When the curing process is 400℃+20s, the Rt value is as high as 70561Ωcm2, and the Cc value is an order of magnitude smaller than that under other conditions, indicating that the coating has the best protective effect at this time. Combined with the experimental analysis of the electrochemical parameters in the Tafel polarization curve, it is found that when the curing condition is 400℃+20s, the electrochemical performance of the coating is better, and the corrosion resistance of the coating is better improved.
 
  SHAPE\*MERGEFORMAT
  Different curing processes have different effects on various properties of the coating. When the curing process is 400℃+2Os, the performance of the coating is optimal. The non-oriented environmentally friendly silicon steel insulating coating covers the silicon steel substrate well, and the coating surface is dense and uniform, and the coating protection rate is as high as 99.53%. In the 5h neutral salt spray test, the percentage of rusted area was only 6%, the electrochemical parameters were significantly better than other conditions, and the insulation resistance reached 300Ω·mm2.

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