Metric 8.8 Hex Head Cap Screw

Metric hex head cap screws, class 8.8 with Zinc Cr3 plating, are high-strength fasteners commonly used in various mechanical and structural applications. These fasteners are designed according to the DIN 931 and DIN 933 standards, which define the specifications for hex head cap screws with partial threads (DIN 931) and full threads (DIN 933). The class 8.8 rating indicates that these screws are made from medium carbon steel and heat-treated to achieve a tensile strength of 800 MPa and a yield strength of 640 MPa. This makes them ideal for use in applications requiring high-strength fastening.

Zinc Cr3 (Chromium III) plating, also known as trivalent chromium plating, offers significant advantages over traditional hexavalent chromium (Cr6) coatings. One of the primary benefits is the enhanced corrosion resistance it provides to the fastener. Zinc Cr3 plating is more environmentally friendly than Cr6, as it is less toxic and has a reduced environmental impact during the manufacturing and disposal processes. Additionally, Zinc Cr3 plating does not suffer from issues like hydrogen embrittlement, which can affect other coated fasteners. The coating provides a protective barrier against corrosion while maintaining the mechanical properties of the screw, ensuring reliable performance even in moderately corrosive environments.

These screws are used extensively in industries such as automotive, construction, and machinery, where high strength, durability, and corrosion resistance are essential. They are commonly found in automotive engines, machinery parts, structural steelworks, and outdoor equipment. The Zinc Cr3 plating ensures these fasteners perform well in environments exposed to moisture, salt, and other corrosive elements. They are also used in applications where a more sustainable and eco-friendly fastening solution is required, as the trivalent chromium process is less harmful to both human health and the environment.