During electrophoresis, what are the different effects of the setting of positive and negative electrodes on the formation of surface coatings on magnesium alloys and iron parts?
Publish Time: 2024-12-10
During electrophoresis, the setting of positive and negative electrodes has a significant and complex effect on the formation of surface coatings on magnesium alloys and iron parts.
For magnesium alloys, due to their high chemical activity, their electrode reactions are unique in the electrophoresis system. When magnesium alloys are used as cathodes, under the action of the electric field, the cationic resin particles in the electrophoresis coating move to its surface and deposit. In this process, hydrogen evolution occurs at the cathode, and the generated hydrogen may affect the bonding force between the coating and the surface of the magnesium alloy. If the hydrogen evolution is too intense, it may cause defects such as pinholes in the coating, reducing the protective performance of the coating. However, the appropriate cathode setting can use the electric field force to make the coating particles uniformly adsorbed on the surface of the magnesium alloy, which is conducive to the formation of a continuous coating with relatively uniform thickness. In addition, during the cathode electrophoresis process, the surface of the magnesium alloy will undergo some micro-electrochemical changes due to the potential difference, making it easier for the coating particles to adhere to its surface and undergo a curing reaction, thereby improving the adhesion and corrosion resistance of the coating.
When iron parts are used as cathodes or anodes during electrophoresis, they are different from magnesium alloys. When iron parts are used as anodes, iron will undergo oxidation reactions to form iron ions that enter the electrophoresis liquid. On the one hand, this may cause changes in the composition of the electrophoresis liquid, affecting the stability of the coating and the quality of the coating; on the other hand, the oxidation of the iron surface will change its surface roughness, which is beneficial to the adhesion of coating particles to a certain extent. However, if the oxidation is excessive, a loose oxide layer will be generated, which is not conducive to the formation of a dense coating. When iron parts are used as cathodes, similar to magnesium alloys, coating particles move and deposit on their surfaces, but because the chemical stability of iron is relatively high, its hydrogen evolution reaction is not as violent as that of magnesium alloys, so there are relatively few defects caused by hydrogen generation during the coating formation process. At the same time, cathode electrophoresis can better control the potential of the iron surface, so that the coating particles can be deposited on the surface in an orderly manner, which is conducive to the formation of a smooth, flat coating with good protective properties.
In short, the setting of positive and negative electrodes has a crucial influence on the formation of surface coatings of magnesium alloys and iron parts during electrophoresis. In the actual electrophoresis process, it is necessary to comprehensively consider multiple factors such as the characteristics of magnesium alloys and iron parts, the performance requirements of the required coatings, and the types of electrophoresis coatings, and accurately adjust the setting parameters of the positive and negative electrodes, such as voltage, current density, etc., to achieve the formation of high-quality coatings on the surfaces of magnesium alloys and iron parts, thereby meeting the performance requirements of magnesium alloys and iron parts after electrophoresis treatment in different industrial application scenarios.
