Cathodic electrophoretic paint is widely used in painting industry because of its environmental protection, safety and high quality. But any good product, only on the basis of reasonable technology, equipment, good maintenance and management, can well reflect its value. Therefore, mastering the correct use of electrophoretic paint is one of the necessary skills for our front-line managers. Before, we Shared with you how to effectively filter electrophoretic paint. Today, we are going to share with you the role of anode system in cathodic electrophoretic paint.

  In cathodic electrophoresis, the electrophoretic coating is a cationic (positively charged) resin and pigment paste, and the coating (workpiece) is used as the cathode. It is the main means to improve the service life (corrosion resistance) of products (such as car body). The initial reaction on the cathode is the formation of hydrogen and hydroxide ions (OH-) by water electrolysis. This reaction leads to the formation of a highly alkaline interface layer on the surface of the cathode, which causes positively charged particles to agglutinate on the cathode. The cation (resin and pigment) reacts with hydroxide ions (OH-) to produce coating deposition.

  Electrodeposition reflects that the electrochemical reaction at the poles is synchronous, and oxygen and organic acids are continuously produced in the anode region. If these acids are not removed in time, they will enter the tank and lower the pH value, affect the stability of process parameters, affect the permeability and coating performance, and increase the resolubility, as well as the abnormal phenomena such as paint film needle hole and film thin.

  There are two ways to remove free acids from the tank: adding unneutralized or partially neutralized cathodic electrophoretic coatings, and using an anode diaphragm system. The antecedent method is expensive and not conducive to stable control, so the antecedent membrane system method is commonly used in industrial mass production, especially in the large cathodic electrophoretic coating line.

  The anode diaphragm system is to seal the anode on a washable anode cover. The anode cover is made of non-conductive material, and the open surface (plate electrode cover is towards the side of the coated material, and all sides of the tube electrode can be regarded as open surface) is equipped with ion selective diaphragm. Anode has plate type, tube type and arc type. The anode cover is covered with a cationic selective semi-permeable film that allows only acid to pass through and is impossible to return to the tank. The membrane anode system, through the discharge of the anode liquid, can keep the acidity balance in the tank during the electrophoresis.   
  The anodes circulation line must be made of stainless steel or plastic with pH resistance of 2-5 organic acids. The circulation amount of anodic liquid is 6~10 L/min per square meter of effective polar area, and the anode is continuously washed to remove anions such as organic acids.

In daily management, the main job of the front-line manager is to monitor the color and conductivity of the anode liquid. Normal indicators are generally as follows:
Anodic liquid color: colorless or light yellow.
The conductivity is 500~1000 microns /cm. When the conductivity is higher than the upper limit, an appropriate amount of anode liquid is discharged, and fresh pure water is added to dilute it.