The core difference in material between solar-specific screws and ordinary screws lies in the targeted design for corrosion resistance. Ordinary screws are mostly made of low-carbon steel or standard stainless steel (e.g., 304 stainless steel). While these materials meet basic needs in indoor dry environments or for short-term outdoor use, they are prone to rust, oxidation, and other damage when exposed to outdoor conditions for extended periods—subject to rain, moisture, ultraviolet (UV) radiation, and industrial pollutants.
In contrast, solar PV systems are typically installed in outdoor environments such as rooftops and open fields, requiring screws to have a service life of over 25 years (matching the lifespan of PV modules). Therefore, solar-specific screws generally use higher-grade corrosion-resistant materials. For instance, mainstream solar-specific screws are often made of 316 stainless steel, which contains molybdenum. This element enables effective resistance to highly corrosive environments like seawater, acid-base fog, and industrial pollution, preventing loose connections caused by rust even in coastal areas, high-humidity regions, or industrial zones. Some high-end products even adopt titanium alloy materials, which further enhance weather resistance while reducing weight—ideal for rooftop installations where load-bearing sensitivity is a concern.
Differences in structural design center on the installation requirements of PV modules, directly affecting installation efficiency and connection stability. Ordinary screws feature a general-purpose structural design: their thread profiles and head shapes (e.g., cross-recessed, hexagon socket) follow standardization, only meeting basic fastening needs without adaptability to PV modules.
Solar-specific screws, however, have differentiated structures tailored to specific steps of PV installation. In terms of head design, they often combine a "flange surface + anti-slip teeth": the flange surface increases the stress-bearing area, preventing pressure damage to the aluminum alloy frames of PV modules during installation; the anti-slip teeth enhance friction with the frame, avoiding screw loosening caused by thermal expansion/contraction or wind-induced vibration over long-term use.
In thread design, some solar-specific screws use fine threads. Compared to ordinary coarse threads, fine threads distribute stress more evenly, reducing stress damage to component brackets and improving shock resistance. Additionally, to meet the connection needs between PV panels and brackets, specific screw lengths are designed for the threaded rods—ensuring that after penetrating the module frame, the exposed length of the rod complies with safety standards, preventing scratches to personnel or damage to components.
Performance differences are the core reason for the two types of screws’ distinct application scenarios, primarily reflected in three dimensions: mechanical strength, weather resistance, and insulation.
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Mechanical Strength: Ordinary screws only meet daily fastening requirements in terms of tensile strength and yield strength (e.g., standard 4.8-grade or 8.8-grade screws). Solar-specific screws, however, must withstand the weight of PV modules, wind/snow loads, and torque forces during installation. Thus, they are often designed with high strength grades (e.g., 10.9-grade or 12.9-grade high-strength stainless steel screws), with tensile strengths exceeding 1000 MPa. This enables them to resist external impacts under extreme weather conditions, preventing component falls caused by screw breakage.
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Weather Resistance: Solar-specific screws must pass rigorous environmental tests, such as salt spray testing (typically requiring over 5000 hours of rust-free performance—far exceeding the 1000-hour standard for ordinary screws) and high-low temperature cycle testing (repeated cycles from -40°C to 85°C). These tests ensure that the material performance and structural stability of the screws remain unaffected by extreme temperature and humidity changes. In contrast, ordinary screws used in solar systems may experience thread seizing or head deformation in the short term.
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Insulation: Some solar-specific screws (e.g., those used for connecting PV junction boxes) undergo insulation coating treatment to avoid leakage risks caused by the electrical conductivity of metal screws. This design is extremely rare in ordinary screws, highlighting the targeted consideration of solar-specific screws for the electrical safety of PV systems.
Differences between the two types of screws are further highlighted in application scenarios and cost-effectiveness. Ordinary screws are suitable for short-term, low-environmental-demand scenarios such as indoor furniture and mechanical equipment, with low costs. However, if used in solar systems, their vulnerability to corrosion and insufficient strength leads to frequent maintenance—increasing operational costs and posing safety hazards such as component detachment or system failure. In the long run, this proves uneconomical.
Although solar-specific screws have a higher unit price than ordinary screws, they can meet the 25-year+ service life requirement of PV systems, reducing maintenance frequency and long-term operational costs while ensuring safe and stable system operation. They represent a "one-time investment, long-term benefit" critical component. For example, in coastal PV projects, ordinary 304 stainless steel screws may rust within 3–5 years, whereas 316 stainless steel solar-specific screws can remain free of significant corrosion for over 20 years, significantly improving system reliability.
In summary, the difference between solar-specific screws and ordinary screws essentially lies in "scenario adaptability." Ordinary screws are general-purpose fasteners, while solar-specific screws are "customized solutions" tailored to the outdoor, long-term, and high-safety demands of PV systems. In solar PV projects, choosing solar-specific screws is not an "excessive investment" but a necessary measure to ensure system safety and extend service life—also reflecting the refined and professional development of the PV industry.
