What is the difference between Dacromet screws and hot-dip galvanized screws

Dacromet and hot-dip galvanized screws are very good. They are suitable for harsh outdoor environments and are very resistant to salt spray experiments. We first need to understand their meaning and then talk about their price difference.
Dacromet is named as zinc chromium coating in China. It is a new type of anticorrosive coating with zinc powder, aluminum powder, chromic acid and deionized water as the main components;
Hot-dip galvanizing is an effective method of metal anti-corrosion, mainly used in metal structure facilities in various industries. It is to immerse the derusted steel parts in a molten zinc solution at about 500℃, so that the surface of the steel parts is attached with a zinc layer, so as to achieve the purpose of anti-corrosion;
Compared with hot-dip galvanizing, Dacromet has obvious advantages. Hot-dip galvanizing is also electro-galvanizing, because hydrogen embrittlement will inevitably occur during pickling and electroplating, and Dacromet's entire process does not involve electrochemistry, and Dacromet's rust removal is by mechanical shot blasting, so Dacromet will not have any hydrogen embrittlement.
Passivation is required after hot-dip galvanizing, but passivation is generally carried out at room temperature, and the highest temperature will not exceed 100°C, so there must be crystal water in the passivation film, so the passivation film of hot-dip galvanizing It is not resistant to high temperatures. Generally, it will peel and crack at 70°C because of the presence of crystal water in the film. The film forming temperature of Dacromet is relatively high (about 280°C), so during the preheating process, the water in the film has already evaporated. Therefore, Dacromet's film is denser than the passivation film, so it has better corrosion resistance, especially high temperature corrosion.
After all, hot-dip galvanizing is also electroplating, so there will be a problem of power line distribution. Dacromet is a kind of coating, so it can be coated by spraying, centrifugal drying, and dipping. The coating is more uniform than electroplating.
Dacromet is more environmentally friendly than hot-dip galvanizing.
The disadvantage of Dacromet is that it contains chromic anhydride, which pollutes the environment like electroplating. In addition, Dacromet's zinc powder has high requirements and high manufacturing costs. Finally, the sintering temperature is higher and the cost is higher. But compared to hot-dip galvanizing, Dacromet is still very cheap.
Hot-dip galvanized screws generally can reach 400-500 hours in salt spray test, and the coating is very thick and generally reach 50-80u, so the hot-dip galvanized nuts must be reamed and then hot-dipped. If it is installed on the equipment, the hole must be reamed to leave a good margin. Generally, the hot-dip galvanized screw ranges from 2.5 yuan to 5 yuan per kilogram, depending on the difficulty of the screw you are processing and what product it is. Generally, flat spring washers are more expensive and generally at least 4-5 yuan per kilogram. , And now there are fewer and fewer hot-dip galvanizing factories. Because of the environmental protection now, the number of hot-dip galvanizing factories is decreasing year by year, and the processing cost is getting more and more expensive. Hesitating serious pollution is now gradually replaced by Dacromet.

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