Titanium anode for electrophoretic coating

What is Titanium anode for electrophoretic coating?

Titanium anodes are commonly used in electrophoretic coating processes, a type of electrochemical deposition process. During electrophoretic coating, the anode is used to attract negatively charged particles to the surface of a substrate. The negatively charged particles are then suspended in a coating solution and drawn to the anode, where they are deposited on the substrate. It is a popular choice in electrophoretic coating processes because it is corrosion resistant, has a low electrical resistance, and is relatively inexpensive.

Parameter requirements

Automotive coating technology: Titanium anode systems in cathodic electrophoresis

Cathodic electrophoresis is a coating process commonly used in car body manufacturing, and it is the main means to improve the service life (corrosion resistance) of the car body. In cathodic electrophoresis, the electrophoretic paint used is cationic (positively charged) resin and pigment paste, and the coated object (body) is used as the cathode. The initial reaction at the cathode is the electrolysis of water to form hydrogen and hydroxide ions (OH-), this reaction results in an over-based interfacial layer on the cathode surface, allowing positively charged particles to agglomerate on the cathode, cations (resins and pigments) ) reacts with hydroxide ions (OH-) to produce coating deposition.

Organic acids are continuously produced in the anode zone:

If these acids are not removed in time, they will enter the bath to reduce the pH value, affect the stability of the process parameters, affect the penetrability and coating performance, and increase the resolubility. There are two ways to remove free acid from the bath: adding an unneutralized or partially neutralized cathodic electrocoat and using an anode diaphragm system. The anode diaphragm system method is generally used, especially in large cathodic electrophoretic coating lines.

Composition of the anode system

The anode system consists of two parts: an anolyte system and an anode power supply. The anolyte system is the main part of the anode system. It consists of an anode diaphragm system, an anolyte round-trip circulation pipeline, a pump, an anolyte tank, a conductivity, and turbidity controller, a Deionized water supply pipeline, and other components.

The anode diaphragm system is to seal the anode on a washable anode cover. The pole cover is made of non-conductive material. The open side (the side of the plate electrode cover facing the object to be coated. The surrounding area of the tubular electrode can be regarded as an open surface) is equipped with Ion selective membrane. Anodes are available in the form of plate type, tubular type, arc type anode, etc. Among them, the tubular type anode is currently the most widely used, and the following highlights:

The tubular anode unit is composed of an anode cover (including an ion exchange membrane) and an anode and is an alternative to the plate anode in the past. Its structure is compact, the membrane resistance is small, the power consumption is low, the swimming force is high, the unit membrane area is large, the service life is long, and the maintenance and management are convenient. Due to its small size and lightweight, it can be installed on the side, bottom, or upper part of the electrophoresis tank to meet the requirements of different coating processes. The anode electrode material is generally made of 316L stainless steel, and the thickness is preferably not less than 3.2mm. Under normal circumstances, the anode dissolves slowly, and its life depends on the productivity of the electrophoresis tank.

Advantage of Titanium electrodes for Electrophoretic paint

Cathodic electrophoresis is a coating process commonly used in car body manufacturing, and it is the main means to improve the service life (corrosion resistance) of the car body. In cathodic electrophoresis, the electrophoretic paint used is cationic (positively charged) resin and pigment paste, and the coated object (body) is used as the cathode.

Stainless steel anodes rely on passivation to work, but the spark dissolution of stainless steel and the formation of passivation films are greatly affected by pulse currents, which are difficult to control in actual production. The probability life of the anode can reach several years. In order to prolong the service life of the anode, a titanium electrode of ruthenium oxide or titanium-based oxide can be selected.

The life of a Ti plate coated with ruthenium oxide is several times longer than that of stainless steel anodes, but the initial investment is also higher than that of stainless steel. Since the chlorine content is very obvious to the corrosion of stainless steel anodes, and the chlorine content has no effect on Ti-based oxide titanium anodes, it can also be used. Ti-based oxide-coated anodes are dimensionally stable anodes, and only a small amount of activity is required during the working process. Coating loss, Ti substrate is always in a loss-free state in production. After the anode is deactivated, only the active layer needs to be re-coated, and the Ti substrate can be used repeatedly, which can save a certain amount of money. The titanium anode has a long service life. Using this anode to replace the stainless steel anode can avoid frequent replacement of the anode, which is conducive to stable and normal production and simplified management.

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