Overview: Small Component, Big Impact

In solar photovoltaic mounting systems, stainless steel hex bolts play a vital role. As the core fasteners connecting PV modules, mounting structures, and buildings, their quality directly affects the structural safety and service life of the entire power plant. With the continuous rise in global PV installed capacity, the market demand for stainless steel hex bolts is also showing steady growth.

According to industry research institutions, the global solar panel fastener market was valued at US$625 million in 2024 and is projected to reach US$841 million by 2031, at a compound annual growth rate (CAGR) of approximately 4.3%. Among these, stainless steel fasteners are widely used in the PV industry due to their excellent corrosion resistance and mechanical strength.

Part One: Technical Characteristics – Why Choose Stainless Steel?

1. Excellent Corrosion Resistance

PV power plants are typically installed outdoors,长期 exposed to wind, rain, sunlight, humidity, and other natural conditions. Ordinary carbon steel bolts are prone to rust and corrosion, while stainless steel hex bolts (especially SUS304 and SUS316 materials) offer superior oxidation and corrosion resistance, ensuring a service life of more than 25 years.

2. High Strength and Reliability

PV mounting systems need to withstand wind loads, snow loads, and extreme conditions such as earthquakes. Stainless steel hex bolts have high tensile and shear strength, meeting performance requirements of grade A2-70 (equivalent to 70-grade), ensuring secure and reliable connections. In dynamic structures such as tracking systems, high-quality stainless steel fasteners are key to guaranteeing long-term stable operation.

3. Anti-Loosening Design

Given the long-term operation of PV systems under dynamic loads such as wind-induced vibration, anti-loosening design is critical. In practice, combinations of “bolt + spring washer + flat washer + nut” are commonly used, or specialized bolts with anti-loosening coatings are employed to prevent loosening under vibration.

4. Weather Resistance and High-Temperature Tolerance

Stainless steel hex bolts maintain stable mechanical performance over a wide temperature range from -40°C to 85°C, meeting the installation requirements of PV systems in different climatic conditions worldwide.

Part Two: Practical Applications – From Module Fixation to Mount Connection

1. Connection Between PV Modules and Rails

In rooftop distributed PV projects, stainless steel hex bolts are often used to secure PV modules to aluminum rails via clamps. For example, in a rooftop distributed PV project in Anhui Province, the procurement list clearly included “M8×25 stainless steel SUS304 bolts with nuts” for clamp connections, totaling 848 sets.

2. Mount Structure Assembly

Mounting systems for large-scale ground power plants are typically assembled from C-section steel or aluminum profiles, with stainless steel hex bolts as the primary fasteners for structural connections. In a PV material procurement project in Hebei Province, tens of thousands of M10×30 and M10×80 hex bolt assemblies (Q235B hot-dip galvanized, with 2 flat washers, 1 spring washer, and 1 nut) were ordered. Although the main material is carbon steel, stainless steel is generally used in key load-bearing areas and locations with higher corrosion risk.

3. Special Scenario Applications: Balcony PV and Micro Systems

For the rapidly growing balcony PV market in Europe, some manufacturers have introduced specialized stainless steel hex eye bolt kits. For instance, NuaSol’s M10×250mm stainless steel hex eye bolt, equipped with an adapter plate and EPDM sealing gasket, is specifically designed for balcony PV systems, with single-set load capacity meeting the installation requirements of micro PV power plants. The product is made of SUS304 stainless steel, with a 7mm hex head, total length of 250mm (threaded portion 80mm), adapter plate size 30×82mm, individual weight 0.76kg, supplied in packs of 10 sets.

Part Three: Industry Trends – Standardization of Specifications and Material Upgrades

1. Standardization of Specifications

From multiple procurement announcements, it is evident that the PV industry’s requirements for stainless steel hex bolt specifications are becoming increasingly standardized. Common specifications include:

2. Surface Treatment and Coating Technologies

To further enhance corrosion resistance, some stainless steel bolts undergo special surface treatments. Professional fastener suppliers such as CHAVESBAO offer hot-dip galvanizing (HDG) and zinc-nickel (Zn-Ni) coating services to suit extreme corrosive environments such as coastal and high-humidity areas. Additionally, zinc-nickel coatings can be tailored to different corrosion resistance levels according to project requirements.

3. Pre-Assembled Supply

To improve on-site installation efficiency, suppliers generally offer pre-assembled kits—bolts, flat washers, spring washers, and nuts pre-assembled and ready for direct use. This approach significantly reduces material management complexity and installation labor hours, achieving cost savings and efficiency gains.

4. Green Manufacturing and Low-Carbon Transition

With the advancement of the 14th Five-Year Plan for Raw Materials Industry Development, the fastener industry is transitioning toward green and low-carbon manufacturing. By 2025, energy consumption per unit of output value in the industry is expected to decrease by 18%, driving environmentally friendly upgrades in stainless steel fastener manufacturing processes.

Part Four: Product Example – Unirac 310751 Roof Mount Hex Bolt

Unirac’s 310751 roof mount hex bolt is a representative product in the PV industry. The product is made of stainless steel with pre-applied thread-locking adhesive, featuring the following characteristics:

This product is fully designed with electrical grounding requirements in mind, supporting proper equipment grounding and reducing electrical fault risks. At the same time, its compatibility with torque wrenches allows installers to make precise torque adjustments, ensuring each connection point is securely tightened without damaging materials.

Part Five: Selection Recommendations

When selecting stainless steel hex bolts for actual PV projects, the following factors should be considered:

Environmental conditions: SUS304 is sufficient for inland areas; SUS316 is recommended for coastal or high-corrosion environments

Load requirements: Calculate required bolt strength and specifications based on design wind and snow loads

Anti-loosening needs: Prioritize products with anti-loosening washers or pre-applied anti-loosening coatings

Installation convenience: Choose pre-assembled kits to significantly improve construction efficiency

Certification requirements: For export projects, ensure products comply with local certification standards (e.g., UL2703)

Packaging and delivery: For large projects, selecting suppliers that offer customized packaging (e.g., anti-rust bags, wooden cases) and assembly services can effectively reduce on-site management costs

In a Nutshell

Though small, the stainless steel hex bolt is an indispensable “joint” for PV power plants—choosing the right material, using the correct specification, and ensuring anti-loosening protection are essential for safe and stable operation for over 25 years. As the PV industry moves toward higher efficiency and intelligence, the application of high-quality stainless steel fasteners will become even more widespread, providing a solid and reliable connection foundation for the global energy transition.