1、 Dacromet process steps:

1. Deoiling: deoiling must be carried out on the surface of products containing vegetable oil. Generally, there are three ways: solvent deoiling, water-based deoiling agent deoiling and high temperature carbonization deoiling. Whether the deoiling is reasonable or not will immediately damage the adhesion and corrosion resistance of the coating.

2. Anti rust treatment for burr removal: all rusty or burred product workpieces are forbidden to be coated immediately. It is necessary to follow the process of anti rust treatment for burr removal. This process is better to use mechanical equipment to prevent pickling passivation and alkali embrittlement. Moreover, pickling passivation and anti rust treatment endanger the corrosion resistance of Dacromet coating due to pickling passivation.

3. Coating: for the cleaned workpiece after degreasing and antirust treatment, the surface coating must be carried out as soon as possible according to the methods of immersion coating, spray painting and painting. During the production and processing of product workpiece coating, the proportion, pH, viscosity, Cr6 + composition, temperature and fluidity of coating solution will immediately endanger the actual effect of product workpiece coating and various characteristics of coating. Therefore, during the whole coating process, it is necessary to adjust the relationship among temperature, water solution index value and centrifuge speed.

4. Pre drying: parts of Dacromet wet film must be dried at 120 ℃ as soon as possible ± Under the temperature of 20 ℃, pre dry for 10-15 minutes (according to the calorific value of the product workpiece), so that the water in the coating solution volatilizes, and the varnish is even.

5. Calcination: the pre baked product workpiece must be calcined at a high temperature of 300 ℃ for 20-40 minutes (according to the calorific value of the product workpiece), and the calcination time can also be reduced by moderately increasing the temperature.

6. Refrigeration: after the calcination of the product workpiece, the subsequent solution or quality inspection must be carried out after sufficient refrigeration of the refrigeration system.

2、 Dacromet technology has the following advantages compared with traditional phosphating treatment and hot dip galvanizing technology

1. Super class corrosion resistance. The controllable photocatalysis maintenance effect of zinc, the shielding effect of zinc and aluminum blocks and the self repairing effect of chromium trioxide promote the Dacromet coating to have high corrosion resistance. It takes 100 hours for the neutral salt spray test of Dacromet coating to etch the coating for 1um, which is 7-10 times higher than the traditional hot dip galvanizing solution, The test time of neutral salt spray can be as long as 1000 hours (the coating with thickness of 8um) or even higher, which can not be achieved by phosphating and hot-dip galvanizing.

2. Good temperature resistance. Because there is no crystal water in the chromic acid polymer of Dacromet coating and the melting point of aluminum and zinc is high, the high temperature corrosion resistance of Dacromet coating is very good. The corrosion resistance of Dacromet coating is almost unaffected when it is used at 300 ℃ for a long time at 250 ℃. However, the passivation treatment film on the surface of phosphating treatment layer is gradually destroyed at about 70 ℃, and the corrosion resistance of Dacromet coating decreases sharply.

3. No hydrogen ductility. In Dacromet's technical treatment mode, there is no process flow such as pickling and passivation, electric deposition and electric oil elimination, so there is no electrochemical corrosion of hydrogen evolution in the whole process of phosphating treatment, so it is not easy to cause alkali embrittlement of materials. Therefore, it is especially suitable for solving ductile parts and high toughness product workpieces.

4. Excellent recoat ability. Dacromet coating is dark gray in appearance, and has excellent combination with plate and various architectural coatings. It can be used as the overall surface layer and the bottom layer of various architectural coatings. It is often used as the bottom layer of architectural coatings to replace acid pickling and phosphating with environmental pollution in the production and manufacture of vehicles in the United States and Japan, and further improve the overall corrosion resistance.

5. Avoid electrochemical reaction to aluminum. Due to the different potential difference between metal materials, electrochemical corrosion will occur. For the hot-dip galvanized coating, whether it is iron-based or aluminum based, its safety protection will produce photoelectrocatalysis and greatly reduce the corrosion resistance.