M6 automotive screws are zinc-nickel alloy black high salt spray washer combination screws, which are high-performance fasteners designed for harsh environments. The following is an introduction to its core functions and key requirements.
1. Core functions
(1) High-strength fastening and anti-loosening
Mechanical properties: Meet ISO 898-1 or DIN 933 standards, tensile strength ≥8.8 (or customized 10.9/12.9), to ensure that it does not loosen under automotive vibration conditions.
Combination design: Integrated washers provide uniform pressure, reduce the risk of loosening, and simplify the assembly process.
(2) Extreme environment corrosion resistance
Zinc-nickel alloy plating: zinc-nickel alloy + black passivation treatment, salt spray test ≥720 hours (neutral salt spray test ASTM B117), suitable for coastal, snow melting agent, and other high-salt environments.
Black surface treatment: Takes into account both corrosion resistance and aesthetics, meeting the requirements of automotive exterior parts.
(3) Compatibility and sealing
Material of washers: stainless steel or galvanized steel washers, which work together with screws to prevent corrosion; fluororubber washers can be used for special working conditions.
Sealing assistance: The washer forms a micro seal after compression to prevent water vapor/corrosive media from invading the thread.
2. Key performance requirements
(1) Materials and processes
Substrate: carbon steel (such as 35K, 45 steel) or alloy steel, reaching performance level after heat treatment.
Coating thickness: zinc-nickel alloy layer 8-12μm, black passivation film 2-5μm, no risk of hydrogen embrittlement (baking and dehydrogenation after electroplating).
(2) Environmental adaptability
Temperature range: -40℃ to +120℃, stable coating, and gasket elasticity maintained.
Chemical resistance: resistant to engine oil, brake oil, weak acid, and alkali.
(3) Assembly reliability
Torque coefficient: preset installation torque value, the washer must ensure torque consistency.
Reusability: After 3 disassembly and assembly tests, the elastic attenuation rate of the gasket is ≤10%.
3. Application scenarios
Key parts: chassis components, battery boxes, exhaust systems, electrical grounding, etc.
Alternative scenarios: long-life, high-safety connection points that ordinary galvanized screws cannot meet.
4. Notes
Testing standards: Salt spray report, torque test data, and material certification are required.
Special requirements: If used for aluminum alloy parts, galvanic corrosion protection is required.
This screw meets the core needs of the automotive industry for high strength, high corrosion resistance, and convenient assembly through the triple guarantee of "plating + structure + material", and is a cost-effective solution for harsh environments.
