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Author: Site Editor Publish Time: 2026-02-27 Origin: Site
Meta Description: Discover the critical role of bolts, nuts, and washers in solar ground mounting systems. Learn about corrosion resistance, anti-loosening technology, material selection, and installation best practices to ensure long-term structural integrity.
Body Text
When specifying a solar ground mounting system, most of the attention goes to the major structural components: the piles, the rails, and the module clamps. However, holding this entire structure together is an army of small but mighty components—the fasteners.
Bolts, nuts, washers, and screws may represent a small fraction of the total project cost, but their failure can lead to catastrophic results: module damage, downtime, safety hazards, and costly repairs. In the demanding environment of a solar farm, where arrays must endure wind, rain, snow, and temperature swings for 25 years or more, fasteners are not a commodity item; they are a critical engineering element.
This article explores the specialized world of fasteners for solar ground mounting systems, covering material science, anti-loosening technology, and the standards that ensure a lifetime of reliability.
Unlike fasteners used in indoor applications or sheltered environments, those in a ground-mount solar array face a unique set of challenges. They must perform flawlessly for decades in one of the most demanding environments imaginable: the great outdoors.
The primary enemy of any outdoor metal component is corrosion. Solar fasteners are constantly exposed to moisture, humidity, and temperature fluctuations. In coastal areas or regions where roads are salted, the presence of chlorides accelerates the corrosion process dramatically .
To combat this, material selection is paramount:
Stainless Steel: Grades like SUS304 are common in many photovoltaic projects, offering excellent resistance to oxidation and corrosion . For harsher environments, particularly near coastlines, 316 stainless steel is often specified due to its molybdenum content, which provides superior resistance to chloride-induced pitting and corrosion .
Zinc-Nickel Alloy & Hot-Dip Galvanizing: For carbon steel fasteners, coatings are essential. Zinc-nickel plating offers a high level of sacrificial protection. Hot-dip galvanizing, where the fastener is coated in a thick layer of zinc, is another standard method. The zinc corrodes preferentially, protecting the underlying steel in a process known as cathodic protection . Industry standards often require coatings to pass rigorous salt spray tests, such as 1440 hours of testing per DIN EN ISO 9227 to ensure longevity .
Avoiding Contact Corrosion: It is not enough for the fastener itself to be corrosion-resistant. Engineers must also consider the interface between different metals. When a stainless steel bolt contacts an aluminum rail, there is a risk of galvanic corrosion. Using appropriate washers or isolators can prevent this destructive electrochemical reaction .
Solar arrays are living structures. They vibrate with the wind, and their components expand and contract with daily and seasonal temperature changes . These dynamic forces constantly work to loosen standard threaded fasteners. A loose bolt can lead to increased stress on other components, structural misalignment, and eventual failure.
To ensure long-term clamping force, solar fasteners employ several anti-loosening features:
Nyloc Nuts (Nylon Insert Lock Nuts): These nuts have a nylon collar at the top that deforms elastically as the bolt is threaded through, creating high friction that resists vibration-induced loosening .
Spring Washers and Serrated Washers: These washers provide tension and a mechanical interlock between the nut/bolt head and the mounting surface, maintaining friction even as the structure settles or vibrates .
Thread-Locking Adhesives: Liquid adhesives applied to the threads cure to form a tough, thermoset plastic that bonds the mating threads together, effectively locking them in place .
A solar ground mounting system utilizes a variety of fasteners, each designed for a specific function.
These are the workhorses of the system, used to connect rails to posts, splice rails together, and attach cross-bracing. They are typically hex-head bolts or flange bolts, paired with compatible nuts. For large-scale projects, the mechanical properties are critical. Specifications often call for Grade 8.8 or higher steel, which denotes a specific tensile strength . A typical "bolt set" includes the bolt, a nut, a flat washer, and a spring washer (often described as "one flat, one spring, one nut") .
As the name suggests, these are U-shaped fasteners with threaded ends. They are invaluable for clamping cylindrical components or for attaching modules to round pipe supports in certain ground mount designs. U-bolts provide a secure, adjustable connection point and are commonly used in systems designed for quick installation .
In modern, high-volume solar manufacturing, speed is money. Self-clinching fasteners, sometimes referred to by brand names like Flangeform, are designed for rapid, permanent installation into sheet metal. They are pressed into place, displacing material to form a strong, captive nut or stud without the need for access to the back side of the panel. This makes them ideal for assembling the cold-formed steel sections commonly used in utility-scale tracker systems, enabling automated production lines to install millions of fasteners efficiently .
In any solar PV system, the National Electrical Code (NEC) requires a continuous ground path to protect against shock and lightning. This means the metallic mounting structure must be electrically bonded together. Special bonding fasteners, often with sharp cutting teeth (star washers) that bite into the anodized coating of aluminum rails, are used to create this conductive path. These screws must engage a certain number of threads—NEC 250.8 requires a minimum of two full threads engagement for machine screws—to ensure a reliable, long-lasting connection .
Choosing the right fastener is only half the battle; proper installation and quality control are equally vital.
Torque Control: Most fasteners in a solar ground mount require a specific torque to achieve the correct clamping force. Under-torquing can lead to loosening, while over-torquing can strip threads or break the bolt. Installers must use calibrated torque wrenches and follow the engineering specifications.
Hydrogen Embrittlement: High-strength steel fasteners are susceptible to hydrogen embrittlement, a phenomenon where hydrogen atoms make the metal brittle and prone to cracking under stress. This can occur during the plating process. Reputable manufacturers employ strict controls, such as baking the fasteners after plating, to eliminate this risk .
Material Verification: For large projects, quality assurance may involve material testing to verify that the fasteners meet the specified grade and coating thickness. For example, a procurement specification might require hot-dip galvanization with an average thickness of 50 micrometers or more .
In the pursuit of lower levelized cost of energy (LCOE), it can be tempting to cut costs on ancillary components like fasteners. However, as the solar industry matures, the focus is shifting from initial capital expenditure to long-term reliability and performance.
The fasteners used in a solar ground mounting system are precision-engineered components designed to withstand decades of environmental assault and dynamic stress. They are the critical links in the structural chain. By understanding the demands of corrosion resistance, the necessity of anti-loosening devices, and the importance of quality standards like ISO 898 for mechanical properties and ISO 1461 for galvanized coatings, project developers can ensure the long-term health of their investments .
At Haina Fastener , we source only the highest quality fasteners for our solar ground mounting solutions, ensuring that every connection is as durable as the overall structure. [Contact our engineering team] to discuss your project requirements and learn how we build reliability from the ground up.
