Dacromet Bolt Treatment Technology

Dacromet surface treatment is a mature and widely promoted environmentally friendly surface treatment technology. Compared with traditional electroplating and hot-dip galvanizing processes, Dacromet treatment is more in line with modern environmental requirements and belongs to a chromium-free eco-friendly treatment technology. Its core advantages are as follows:

Excellent corrosion resistance: The thickness of the Dacromet coating is only 4-8μm, but its rust prevention effect is more than 7-10 times that of traditional electroplating. Fasteners such as hex nuts and washers treated with the Dacromet process can withstand a salt spray test for more than 1200 hours without red rust. Moreover, the thread fit accuracy is not affected, and the screwing smoothness is consistent with that of ordinary fasteners.

No hydrogen embrittlement risk: This is one of the most prominent advantages of Dacromet, making it particularly suitable for processing high-strength screws. Fasteners with a strength grade of Grade 8.8 and above are all applicable. Traditional electroplating processes are prone to hydrogen embrittlement, which may cause high-strength bolts to fracture under stress. In contrast, the Dacromet treatment process has no hydrogen evolution reaction throughout, fundamentally eliminating the hidden danger of hydrogen embrittlement.

High-temperature corrosion resistance: The heat resistance temperature can reach above 300℃, and the coating performance remains stable at this temperature. However, ordinary electroplated zinc coatings are prone to peeling and falling off when the temperature reaches 100℃, leading to failure and scrapping.

Strong coating adhesion and high finish: The Dacromet coating is closely combined with the fastener substrate, featuring extremely strong adhesion. At the same time, the surface is smooth and delicate, allowing for secondary coloring directly on the coating to meet different appearance requirements.

Environmental friendliness and controllable cost: During the entire production and coating process of Dacromet treatment, no wastewater or waste gas is discharged, only a small amount of solid waste is generated. This significantly reduces the pressure of three-waste (wastewater, waste gas, solid waste) treatment and greatly lowers the environmental treatment cost compared with traditional electroplating.

Compatible with multiple strength grades: Fasteners of different strength grades (whether Grade 4.8, Grade 8.8, etc.) can be processed in the same treatment environment under the premise of ensuring material compatibility and unified pre-treatment processes. There is no risk of quality instability caused by material differences.

Suitable for high-grade high-strength bolts: Ultra-high-strength bolts of Grade 12.9 can also be treated with Dacromet. After treatment, the thread fit is smooth. The matching performance between standard Dacromet bolts and nuts is consistent with that of ordinary fasteners, eliminating the need for nut reaming and not affecting assembly efficiency.

Suitable for small-size hex socket head cap screws: Due to their special structure, small-size hex socket head cap screws are prone to deformation of the hex socket, reduced strength, and inability to guarantee dimensional accuracy during hot-dip galvanizing. In contrast, Dacromet treatment is carried out at a low temperature (usually around 200℃), which will not reduce the size of the hex socket's opposite sides or damage the thread accuracy. During assembly, the wrench fits well, completely solving the corrosion prevention problem of small-size hex socket head cap screws and making it an optimal corrosion prevention solution for such parts.

Application of Dacromet Screw Technology in the Heavy-Duty Truck Industry

Meeting the demand for high-strength fasteners: One of the core differences between Dacromet and hot-dip galvanizing is the absence of hydrogen embrittlement risk. A large number of high-strength screws are used in key parts of heavy-duty trucks (such as the chassis and engine compartment), and such screws are extremely sensitive to hydrogen embrittlement. Therefore, Dacromet treatment has become the mainstream choice-it not only ensures excellent corrosion resistance but also avoids the fracture risk caused by hydrogen embrittlement, safeguarding driving safety.

Balancing rust prevention and appearance requirements: Hot-dip galvanized coatings are prone to zinc nodules and burrs, resulting in poor finish. In contrast, Dacromet coatings are uniform, delicate, and neat in appearance. Therefore, for automotive parts installed indoors that require both good rust prevention and a neat appearance (such as interior fasteners and cab connecting components), Dacromet Bolt are more widely used.

Adapting to thin-coating assembly requirements: The Dacromet coating is thin, so it will not affect the assembly clearance of precision parts due to coating thickness, making it particularly suitable for the fastening scenarios of various precision equipment on trucks. At the same time, the dry indoor environment of trucks with few corrosive media is an ideal application environment for Dacromet screws. Therefore, they have a wide range of application scenarios in the heavy-duty truck industry, and the above are only typical cases.