A new alternative to electroplating - Dacromet technology (2)

A new alternative to electroplating - Dacromet technology (2)

Fourth, the coating process of Dacromet technology

The purpose of the coating operation is to uniformly coat the surface of the steel drum with a layer of Dacromet coating, so that the coating can be made uniform and uniform throughout the steel drum, and the coating is thick and wastes the coating liquid. It also affects the surface quality of the coating, so no matter what method is used for the coating, it is necessary to try to distribute the coating liquid evenly on the surface of the workpiece. Dacromet's coating process is divided into dip coating, drying, spraying, brushing and other methods according to the different methods of painting. When deciding which method to use, the first consideration is whether the coating to be covered on the steel drum is functional or decorative, but also the thickness control, production speed, product shape and required quality. Careful consideration of the above questions will determine which method is best for you.

1. Dip coating

Suitable for small steel drum parts, such as various steel barrel sealers, bucket bottom covers, lifting rings, etc., the barrel parts are generally immersed for ten to twenty seconds, in order to fully form a purified film of hexavalent chromium and steel substrates; When centrifuging and drying, it is necessary to rotate forward and reverse twice, each time for ten to twenty seconds. For special parts, use clamps, and difficult parts should be manually assisted. For example, stir the rods in the centrifuge basket, and the rotation speed should be Fast, in short, to ensure that there can be no liquid, hanging liquid, air bubbles, leaking coating, etc. on the barrel. The final process parameters are determined according to the actual coating effect by repeatedly inverting the sputum and adjusting the drying speed multiple times.

2, spraying, brushing

Generally used for barrel parts, used for difficult dip coating, difficult to centrifuge and dry the barrel. The sprayed coating is uniform, the coating is thick, the bonding force is poor but the finish is good, the corrosion resistance is strong but the efficiency is low, and the construction should pay attention to safety, and the viscosity of the slurry should be appropriately reduced during spraying.

Five, the advantages of Dacromet technology

1. Environmental protection issues

When surface treatment such as electroplating is used due to the use of acid, alkali, and salt, there is always a problem of emissions of three wastes. Dacromet's new coating process is used for surface anti-corrosion, mainly through processes such as degreasing, coating, solidification, cooling, and finished product inspection. The whole process is basically closed. Dacromet is a water-soluble liquid that produces only a small amount of water vapor when it is cured, so it does not produce environmentally harmful substances. There are 15,000 electroplating production plants in the country, with more than 500,000 employees in the industry. There are more than 5,000 production lines and 250-300 million square meters of electroplating area production capacity. The annual output value of the electroplating industry is about 10 billion yuan. According to statistics, China's electroplating industry emits 400 million tons of heavy metal-containing wastewater, 5,000 tons of solid waste and 30 million cubic meters of acid gas. If the Dacromet process is widely used in the electroplating industry, our environment will be well protected.

2, safety production issues

Dacromet coatings are significantly safer than typical solvent-based coatings. Solvent mist can cause fires and endanger workers' health. The Dacromet solution is water-soluble and non-combustible. During the coating and curing process of the barrel, only a small amount of water vapor is generated, and the operator can wear a mask to protect it. For most liquid coatings, bulky gas masks are required.

3, coating performance problems

Compared to electroplating, Dacromet has significant advantages in terms of corrosion resistance and chemical resistance. This is mainly due to the controlled self-sacrificial protection of the Dacromet anti-corrosion coating, the shielding effect of the zinc sheet and the chromium compound, and the dense oxide film formed on the metal surface which is not easily corroded to prevent the metal surface from being prolonged. Rust anti-corrosion effect. The anti-corrosion effect of Dacromet film metal is ten times higher than that of traditional technology. Anti-corrosion principle: controlled sacrificial anode protection (zinc film), purification (chromic acid in the slurry loses crystal water after baking, forms a film on the surface of the barrel, binds zinc and aluminum sheets, thereby improving anti-corrosion ability), shielding effect . The entire coating is about 6 to 10 microns thick, about 0.1 to 0.2 microns thick, and about 60 to 100 layers of protective film, so the Dacromet coating has one big advantage: the surface of the part is scratched, and It does not affect its anti-corrosion performance, because the surface scratch is only scratched several layers, and there are dozens of layers of protective film. The Dacromet coating is therefore more resistant to corrosion (more than 1000 hours of salt spray on iron-based barrels), better chemical resistance, and better resistance to atmospheric corrosion. Its outstanding coating properties make it more and more widely used.

4, production costs

In general, the most significant cost saving method is to reduce the cost of the coating material. Compared to other coatings, Dacromet coatings are not expensive and are more versatile. The market price of domestic Dacromet coatings ranges from 35,000 yuan to 40,000 yuan per ton. If the coating materials are self-made, the key materials such as zinc sheets and aluminum sheets are imported, and the cost per ton is about 20,000 yuan. The price is about 20,000 yuan. When the Dacromet coating is used, it can be automatically coated by a robot and continuously cured in an oven, resulting in higher productivity in the running time. Dacromet coatings fully meet automation requirements, thus reducing labor costs. Because Dacromet coatings are non-hazardous, the waste disposal costs are greatly reduced. Since there is no need to replenish air, the curing oven can use lower energy consumption. In addition, the Dacromet coating system has a lower scrap rate (usually less than 2%). This means that you spend less time and money reworking non-conforming products.

5. Equipment investment problems

The early domestic Dacromet production technology was in the hands of a few people, so the price of the Dacromet production line is indeed very high, and SMEs are unbearable. With the popularity of Dacromet and advances in technology, the price of Dacromet equipment has fallen to normal levels. Dacromet equipment is divided into two types: continuous and intermittent. The former is high in price and high in autonomy. It is the preferred model for manufacturers with large processing capacity; the labor intensity of workers in the latter production process is relatively large, but equipment investment Small, only one-third of the former, its annual processing volume is similar to the former, and it is an ideal model for small and medium-sized enterprises. Because the investment is small, the investment risk is also small. Under normal circumstances, the investment can be recovered in the current year.

6, coating thickness problem

In fact, the thickness of the Dacromet coating is very easy to achieve, and the thickness of the Dacromet coating is proportional to the solids content of the coating liquid used. For a given coating liquid, the thickness of the coating is foreseeable and can be varied by the number of coatings, and the thickness of the coating is proportional to the time of salt spray resistance. The thickness of the coating can be determined according to the requirements of the customer, and it is decided whether to apply one-coating or several-coating in coating.

7, the color of Dacromet coating

In the past, it was difficult to obtain Dacromet coatings of different colors. Generally, it was covered with other colored coatings on the Dacromet coating. Nowadays, Dacromets of different colors have come out.

Above we briefly introduced the situation of Dacromet technology, which is a technology that has developed rapidly in recent years. It is expected that in the near future, we will see that this technology is widely used in the steel drum packaging industry.