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Principle and Application of Fluorozirconic Acid Surface Treatment Technology
info：www.wvchemicalgroup.com | Release time：2023-04-26
Principle, Technical Content, and Application of Fluorozirconic Acid Surface Treatment Technology
1. Principle of Fluorozirconic Acid Surface Treatment Technology
Zirconization technology uses fluorozirconic acid as the main agent, and utilizes the hydrolysis reaction of fluorozirconic acid to form a chemically stable amorphous oxide conversion film on the surface of the metal substrate; The conversion film relies on the strong bonding between zirconium compounds and metal substrates, as well as the strong bonding between polymer compounds in the zirconium solution and the coating, to obtain high-performance metal surface films, thereby achieving excellent adhesion and corrosion resistance. The film formation mechanism on cold-rolled plates is shown in reaction equations (1) and (2).
Fe+3HF? FeF3+3/2H2 （1）
H2ZrF6+2H2O? ZrO2+6HF （2）
Through the corrosion reaction of reaction equation (1), HF is consumed, causing the equilibrium of reaction (2) to shift to the right and form ZrO2. The main components of the film are Zr oxides and hydroxides. During this process, the hydroxyl groups of Zr oxides and hydroxides can bind with polymer compounds, forming organic-inorganic hybrid films with nanoscale thickness at room temperature.
This technology uses zirconium plating solution instead of phosphating solution to pretreat the metal surface, omitting the heating step of heating the tank solution in the phosphating process and reducing energy consumption.
2. Key technologies
At room temperature, the effect of zirconation technology on metal surface treatment exceeds that of traditional heating phosphating treatment process. The existing ambient temperature zirconation technology at home and abroad widely suffers from secondary corrosion or rusting of metal parts. This technology introduces rare earth element cerium into the zirconation pretreatment process. During the film formation process of the zirconation solution with polymer compounds, cerium is doped into the composite zirconation film, making the formed nano thickness zirconation film more dense and uniform in structure. It can effectively prevent secondary oxidation of treated metal parts and solve the problems of excessive corrosion and rusting in the promotion of ambient temperature zirconation technology. When processing medium and low-grade cold-rolled plates, the rust return rate is less than 0.5%, far below the international average level (about 40%).
3. Process flow
The comparison between the ambient temperature zirconium treatment technology and the traditional phosphating process before metal coating is shown in Figure 1 and Figure 2.
The traditional phosphating process usually involves:
Pre degreasing → degreasing → water washing → water washing → surface conditioning → medium temperature phosphating (heating required) → sealing → water washing → water washing → water washing → water washing → drying;
Adopting zirconium based energy-saving technology, the process is usually simplified as follows:
Pre degreasing → degreasing → water washing → water washing → room temperature zirconium solution treatment (without heating) → water washing → drying.
2、 Main technical indicators
1. Energy consumption: 0.5tce/km2 processing area;
2. Section operating temperature: ambient temperature (5-35 ℃);
3. Pre treatment tank capacity: 6t~200t;
4. Daily wastewater volume: ＜ 3t, calculated based on a 6-ton treatment tank;
5. Spray pump power: 44kW/h.
3、 Application Cases
This technology is suitable for the light industry, automotive, home appliances, electromechanical, building materials, equipment manufacturing, aluminum profiles, color coated plates and other metal products industries. It has been promoted and applied in Liaoning, Zhejiang, Jiangsu, Shandong, Tianjin, Guangdong and other places. Its typical users include Mitsubishi Heavy Industries, Haier (Qingdao) Air Conditioning Co., Ltd., Haier Kaikai Refrigeration Equipment Co., Ltd., BYD Auto Manufacturing Co., Ltd., Hitachi Electric Appliances Co., Ltd., FAW Volkswagen Automotive Co., Ltd., Dalian Alice Co., Ltd., Guangzhou Hisense Co., Ltd., China Shipbuilding Industry Corporation, China Aviation Industry Corporation, Shenzhen Foxconn and other enterprises. Taking the construction scale of 5 million refrigeration equipment per year and the renovation of 32 million square meters of coating area as an example, the renovation of the spray equipment can save 4080 tce of energy per year after the renovation, with an annual energy-saving economic benefit of 4.72 million yuan.
1. Principle of Fluorozirconic Acid Surface Treatment Technology
Zirconization technology uses fluorozirconic acid as the main agent, and utilizes the hydrolysis reaction of fluorozirconic acid to form a chemically stable amorphous oxide conversion film on the surface of the metal substrate; The conversion film relies on the strong bonding between zirconium compounds and metal substrates, as well as the strong bonding between polymer compounds in the zirconium solution and the coating, to obtain high-performance metal surface films, thereby achieving excellent adhesion and corrosion resistance. The film formation mechanism on cold-rolled plates is shown in reaction equations (1) and (2).
Fe+3HF? FeF3+3/2H2 （1）
H2ZrF6+2H2O? ZrO2+6HF （2）
Through the corrosion reaction of reaction equation (1), HF is consumed, causing the equilibrium of reaction (2) to shift to the right and form ZrO2. The main components of the film are Zr oxides and hydroxides. During this process, the hydroxyl groups of Zr oxides and hydroxides can bind with polymer compounds, forming organic-inorganic hybrid films with nanoscale thickness at room temperature.
This technology uses zirconium plating solution instead of phosphating solution to pretreat the metal surface, omitting the heating step of heating the tank solution in the phosphating process and reducing energy consumption.
2. Key technologies
At room temperature, the effect of zirconation technology on metal surface treatment exceeds that of traditional heating phosphating treatment process. The existing ambient temperature zirconation technology at home and abroad widely suffers from secondary corrosion or rusting of metal parts. This technology introduces rare earth element cerium into the zirconation pretreatment process. During the film formation process of the zirconation solution with polymer compounds, cerium is doped into the composite zirconation film, making the formed nano thickness zirconation film more dense and uniform in structure. It can effectively prevent secondary oxidation of treated metal parts and solve the problems of excessive corrosion and rusting in the promotion of ambient temperature zirconation technology. When processing medium and low-grade cold-rolled plates, the rust return rate is less than 0.5%, far below the international average level (about 40%).
3. Process flow
The comparison between the ambient temperature zirconium treatment technology and the traditional phosphating process before metal coating is shown in Figure 1 and Figure 2.
The traditional phosphating process usually involves:
Pre degreasing → degreasing → water washing → water washing → surface conditioning → medium temperature phosphating (heating required) → sealing → water washing → water washing → water washing → water washing → drying;
Adopting zirconium based energy-saving technology, the process is usually simplified as follows:
Pre degreasing → degreasing → water washing → water washing → room temperature zirconium solution treatment (without heating) → water washing → drying.
2、 Main technical indicators
1. Energy consumption: 0.5tce/km2 processing area;
2. Section operating temperature: ambient temperature (5-35 ℃);
3. Pre treatment tank capacity: 6t~200t;
4. Daily wastewater volume: ＜ 3t, calculated based on a 6-ton treatment tank;
5. Spray pump power: 44kW/h.
3、 Application Cases
This technology is suitable for the light industry, automotive, home appliances, electromechanical, building materials, equipment manufacturing, aluminum profiles, color coated plates and other metal products industries. It has been promoted and applied in Liaoning, Zhejiang, Jiangsu, Shandong, Tianjin, Guangdong and other places. Its typical users include Mitsubishi Heavy Industries, Haier (Qingdao) Air Conditioning Co., Ltd., Haier Kaikai Refrigeration Equipment Co., Ltd., BYD Auto Manufacturing Co., Ltd., Hitachi Electric Appliances Co., Ltd., FAW Volkswagen Automotive Co., Ltd., Dalian Alice Co., Ltd., Guangzhou Hisense Co., Ltd., China Shipbuilding Industry Corporation, China Aviation Industry Corporation, Shenzhen Foxconn and other enterprises. Taking the construction scale of 5 million refrigeration equipment per year and the renovation of 32 million square meters of coating area as an example, the renovation of the spray equipment can save 4080 tce of energy per year after the renovation, with an annual energy-saving economic benefit of 4.72 million yuan.
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