M6 automotive screws utilize a combination of zinc-nickel alloy, black high-salt spray surface treatment, and washers. It is a high-corrosion and high-strength professional fastener solution. The following is a detailed description of its different surface treatment solutions.
Substrate and thread specifications
Material: carbon steel or alloy steel, hardness level 8.8 and above
Thread specifications: M6× (customized length according to requirements), in line with ISO 898-1/GB/T 3098.1 standards
Washer type: can be matched with F-type flat washers or SPR locking washers (need to clarify the synchronous treatment of spring washers)
Zinc-nickel alloy plating core parameters
Alloy ratio: Ni content 12-16%, is the best anti-corrosion ratio.
Plating thickness: 8-15μm, key stress parts are recommended to be ≥12μm.
Bottom layer treatment: Cyanide-free copper base plating (3-5μm) is required to enhance bonding strength.
Black passivation process
Passivation film type: trivalent chromium black passivation (Cr³⁺ content <0.02% by ELV directive)
Sealing treatment: Nano-silane sealer penetration treatment (improves hand sweat resistance and chemical stability)
Salt spray test standard
Neutral salt spray (NSS): ≥1000h no red rust (ISO 9227 standard)
Cyclic corrosion (CCT): Passed GM9540P 80-cycle test
Scratch spread: Single-side corrosion <1mm (ASTM B117 cross-scratch method)
Mechanical performance guarantee
Hydrogen embrittlement risk control: 200℃×8h dehydrogenation heat treatment (by ISO 4042)
Torque coefficient: 0.12-0.18 (special lubricating coating required)
Washer matching: ensure that the combined torque attenuation after plating is less than 15%
Special environmental adaptability
Temperature range: -50℃~+120℃ (short-term resistance to 150℃)
Chemical resistance: passed the 5%NaOH/3%H₂SO₄ solution immersion test for 96h
This solution is particularly suitable for harsh environments such as new energy battery packs and chassis suspension systems. The cost is about 40-60% higher than that of ordinary galvanizing, but the life cycle can be extended by 3-5 times.
This product complies with relevant standards such as ISO 4042 and DIN 267-10. Please refer to the specific technical requirements of the vehicle manufacturer when using it. It realizes 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.
