Hot-dip galvanizing:
Hot-dip galvanizing involves immersing the rusted steel parts in molten zinc at a temperature of 400-500°C, causing a zinc layer to form on the surface of the steel components, thereby achieving the purpose of corrosion prevention. The surface of hot-dip galvanizing is light gray, rough and not smooth, but the coating is very thick, reaching 30-80 micrometers, resulting in poor thread accuracy for fasteners, but good corrosion resistance, good adhesion, and the surface can withstand high temperatures.
The salt spray test time for hot-dip galvanizing is usually 110-240 hours. The production process has high energy consumption and causes serious environmental pollution. Additionally, due to the high temperature of the hot-dip galvanizing process, it can cause changes in the mechanical properties of 10.9 grade and especially 12.9 grade high-strength bolts, resulting in a decrease in strength. The solution used in the hot-dip galvanizing process contains hydrogen ions, which can cause a small probability of hydrogen embrittlement risk.
Cold galvanizing:
Cold galvanizing involves electrolyzing materials to attach a metal layer to the surface of the metal, making the material surface uniform in texture, resistant to corrosion and wear, and more aesthetically pleasing. The surface of the workpiece is smooth and flat, but the coating is relatively thin, generally within 5 micrometers, so the corrosion protection time is shorter and it is prone to rusting.
The salt spray time for cold galvanizing is 12-72 hours. The production process has high energy consumption and causes serious environmental pollution. Additionally, due to the electrolytic chemical reaction in cold galvanizing, high-strength fasteners can experience hydrogen embrittlement and even fracture, so it is not suitable for 10.9 grade, 12.9 grade, etc., high-strength bolts.
Stainless steel:
Stainless steel screws usually refer to steel screws that have the ability to resist corrosion from air, water, acids, alkalis, salts, or other media. Stainless steel screws are generally not prone to rust, durable, and can be used in fields such as environmental protection equipment, medical equipment, and communication equipment.
The salt spray time for stainless steel is 24-128 hours. The production process has relatively lower energy consumption and causes less environmental pollution. Additionally, due to the electrolytic chemical reaction in cold galvanizing, high-strength fasteners can experience hydrogen embrittlement and even fracture, so it is not suitable for 10.9 grade, 12.9 grade, etc., high-strength bolts.
Dacromet:
Dacromet is a new type of environmentally friendly anti-corrosion process mainly composed of zinc powder, aluminum powder, chromic acid, and deionized water. Dacromet is a new surface treatment technology that is a "green product" compared to traditional galvanizing processes.
The Dacromet coating is much thinner than hot-dip galvanizing, with a layer thickness of only 6-12 μm. The appearance is shiny, generally silver gray, and has good adhesion. Dacromet has a long salt spray test time and does not have a significant impact on the hardness of high-strength steel, nor does it have a hydrogen embrittlement risk.
Superior corrosion resistance: The salt spray test time of Dacromet can reach 240-1200 hours.
High heat resistance: Dacromet can resist high-temperature corrosion and has a heat resistance temperature of over 300°C.
No hydrogen embrittlement risk: Suitable for all high-strength products such as 12.9 grade, 10.9 grade, 8.8 grade, etc.
The production process has lower energy consumption compared to hot-dip galvanizing and causes almost no environmental pollution.
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