White zinc - Hexagon bolt

Overview of White Zinc Hex Bolts

White zinc hexagon bolts are the standard choice for the vast majority of industrial and commercial fastening applications where stainless steel is not required. The "White Zinc" finish is achieved through electro-plating zinc onto the steel, followed by a clear or blueish chromate conversion coating. This process not only delays corrosion but also provides a lubricant effect that assists in installation. The hexagonal head is designed to handle high torque transmission, making these bolts ideal for structural assembly.

Property Classes and Material Specifications

Selecting the correct strength grade is vital for safety. A bolt usually fails due to improper grade selection rather than manufacturing defects. We offer the following grades in white zinc plating:

Grade	Material Type	Typical Application	Tensile Strength
4.8	Low Carbon Steel (Mild)	Non-critical fastening, furniture, fencing, and light maintenance where shear loads are low.	400 N/mm²
8.8	Medium Carbon Steel (Quenched & Tempered)	The industrial standard for "High Tensile" bolts. Used in structural steelwork, automotive engines, and heavy machinery.	800 N/mm²
10.9	Low Carbon Alloy Steel (Quenched & Tempered)	High-stress applications requiring superior strength-to-weight ratios, such as automotive suspension parts.	1000 N/mm²
12.9	Alloy Steel (Quenched & Tempered)	Critical clamping applications like hydraulic clamping and heavy forging machinery.	1200 N/mm²

Quality Control and Certificates

Ensuring the steel grade matches the stamp on the head is our priority. Fastener Core provides EN 10204 3.1 Material Test Certificates (MTC) free of charge upon request. Please note that while MTCs are complimentary, third-party verification services are available at an additional cost.

Common Industrial Uses

White zinc plated hex bolts are versatile and found in numerous sectors:

• Automotive & Transport: Grade 8.8 and 10.9 bolts are extensively used for chassis and engine components.
• Warehousing: Assembly of racking and shelving units (typically Grade 4.8 or 8.8).
• General Machinery: Fastening motors, guards, and casings in indoor factories.
• Consumer Goods: Furniture assembly and DIY hardware due to the clean appearance of the zinc finish.

Frequently Asked Questions

What is the corrosion resistance of White Zinc plating?

White zinc plating (typically 3-5 microns thick) provides moderate corrosion resistance suitable for dry, indoor environments. It protects the steel by acting as a sacrificial anode. In salt spray tests, standard white zinc typically lasts between 24 to 96 hours to white rust, depending on the passivation process. It is not recommended for permanent outdoor use in coastal areas.

Can I use Grade 12.9 bolts in all high-strength applications?

While Grade 12.9 offers the highest tensile strength, it is also more brittle than Grade 8.8. It has lower ductility and is more susceptible to hydrogen embrittlement, especially if the plating process is not carefully controlled (de-embrittlement baking). Therefore, Grade 12.9 should only be used where specifically engineered, rather than simply as a "better" replacement for 8.8.

How do I identify the grade on the bolt?

Hexagon bolts are marked on the head. You will see the manufacturer's mark and the grade number: "4.8", "8.8", "10.9", or "12.9". The dot between the numbers separates the tensile strength (first number) from the yield strength ratio (second number). For example, "8.8" means 800 MPa tensile strength and 80% yield ratio (640 MPa yield strength).