4.8 - Black Zinc - Cross recess pan head screw

Technical Overview of 4.8 Black Zinc Screws

The combination of Grade 4.8 steel and black zinc plating creates a fastener optimized for appearance and cost-efficiency rather than extreme strength. These screws are designed for applications where the primary requirement is to hold lightweight components in place securely, without the need for high torque or heavy load-bearing capacity.

Understanding Grade 4.8 Steel

Material Composition: Grade 4.8 indicates low carbon steel that has not been heat-treated. The "4" represents a tensile strength of 400 N/mm², and the ".8" indicates a yield strength ratio of 80% (320 N/mm²). This makes it softer and more ductile than high-tensile grades like 8.8 or 10.9. Practical Implications: Due to its lower strength, Grade 4.8 is best suited for fastening non-critical components such as covers, panels, and brackets. It should not be used in structural applications or where high vibration could cause the joint to loosen under stress.

Black Zinc Plating Characteristics

Appearance: Black zinc plating is an electro-galvanized coating followed by a black chromate conversion process. This creates a uniform dark grey to black finish that is visually appealing and reduces light reflection. Corrosion Resistance: Black zinc offers moderate protection against rust, suitable for indoor environments and dry conditions. However, it is generally slightly less corrosion-resistant than standard white/clear zinc plating. For outdoor or humid applications, stainless steel or hot-dip galvanized fasteners are recommended.

Quality Assurance

We ensure consistent quality for all our fasteners. An EN 10204 3.1 Material Certificate is available upon request to verify the chemical composition of the steel. Please note that third-party inspection services require an additional fee.

Common Applications

4.8 black zinc pan head screws are widely used in:

• Consumer Electronics: Securing dark-colored plastic housings on audio equipment, gaming consoles, and computer peripherals.
• Electrical Enclosures: Fastening junction box covers and control panel doors.
• Office Furniture: Assembling desks, chairs, and storage units with a modern aesthetic.
• Automotive Interiors: Attaching trim panels and dashboard components where a dark finish is required.

Frequently Asked Questions

What is the difference between black zinc and white zinc?

The primary difference is appearance. White (clear) zinc has a bright silver finish, while black zinc has a dark grey to black finish. In terms of corrosion resistance, white zinc typically performs slightly better in salt spray tests. Black zinc is chosen primarily for aesthetic reasons when a non-reflective, dark fastener is needed.

Can I use Grade 4.8 screws for heavy-duty applications?

No, Grade 4.8 is not recommended for heavy-duty or structural applications. With a tensile strength of only 400 MPa (compared to 800 MPa for Grade 8.8), these screws are designed for light-duty fastening. Using them in high-stress situations could result in failure. Always match the screw grade to the load requirements of your application.

How do I avoid stripping the Phillips drive?

To prevent "cam-out" (the driver slipping out and damaging the recess), ensure you are using the correct size Phillips bit (typically #1 or #2 depending on screw size). Apply firm downward pressure while turning, and use a slow speed setting if using a power driver. Worn or damaged bits should be replaced immediately.