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Colored zinc-plated nuts
Colored zinc-plated nuts are passivated on the basis of electrogalvanizing to form a rainbow-colored passivation film (containing trivalent chromium or hexavalent chromium) with a film thickness of about 0.5-1μm. Its anti-corrosion performance is significantly better than ordinary electrogalvanizing, and the surface color is bright, with both functionality and decorativeness.
Description
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Product definition and core technology
Colored zinc-plated nuts are passivated on the basis of electrogalvanizing to form a rainbow-colored passivation film (containing trivalent chromium or hexavalent chromium) with a film thickness of about 0.5-1μm. Its anti-corrosion performance is significantly better than ordinary electrogalvanizing, and the surface color is bright, with both functionality and decorativeness.
Core materials and characteristics
Material: Q235 carbon steel, Q345 alloy steel, substrate hardness HV150-250, passivation film salt spray test 72-120 hours without white rust, using alkali zinc process or high-quality passivator (such as Bigley Zn-228) can reach more than 96 hours.
Features:
Self-repairing ability: After the passivation film is scratched, the hexavalent chromium component can automatically repair the damaged part;
Environmental protection: Trivalent chromium passivation complies with RoHS 2.0, and hexavalent chromium must comply with REACH regulations;
Color identification: Rainbow colors can be used to distinguish different torque levels or batches (such as the power industry).
Functions and applicable scenarios
Functions:
Long-term resistance to corrosion such as salt spray and acid rain, and the life span is 3-5 times that of ordinary electroplating galvanizing;
Enhance visual recognition and facilitate equipment maintenance and management.
Scenario:
Outdoor power equipment (such as tower bolts), marine engineering (ship deck connection), chemical machinery (tank flange).
Installation and maintenance
Installation:
Use a torque wrench to ensure uniform preload to prevent the passivation film from falling off due to excessive extrusion;
Do not directly contact with active metals such as aluminum and magnesium to prevent galvanic corrosion.
Maintenance:
Avoid using acidic cleaners, and it is recommended to wipe with neutral solvents;
Use with caution in high temperature environments (>100℃), the passivation film may decompose and fail.
Purchase suggestions
For scenarios with high environmental requirements, choose trivalent chromium passivation or chromium-free passivation process;
For high humidity environments, it is recommended to use anti-rust oil to extend the service life.
Comparison and selection guide of the six major nuts
| Type | Electroplated galvanized flange nut | Electroplated galvanized nut | Colored zinc-plated nut | Anti-loosening nut | High-strength blackened nut | Welding nut |
| Core advantages | Dispersed pressure, anti-loosening | Low cost, strong versatility | High corrosion resistance, color identification | Anti-vibration, removable | High strength, high temperature resistance | Permanent connection, convenient |
| Salt spray test | 24-72 hours | 24-72 hours | 72-120 hours | 48 hours (nylon) | 48 hours without red rust | 48 hours (galvanized) |
| Applicable temperature | -20℃~80℃ | -20℃~80℃ | -20℃~100℃ | -56℃~170℃ (all metal) | -40℃~200℃ | -20℃~200℃ |
| Typical scenarios | Pipe flange, steel structure | General machinery, indoor environment | Outdoor equipment, humid environment | Engine, vibration equipment | High temperature machinery, vibration equipment | Automobile manufacturing, construction machinery |
| Installation method | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Torque wrench tightening | Welding fixation |
| Environmental protection | Cyanide-free process complies with RoHS | Cyanide-free process complies with RoHS | Trivalent chromium is more environmentally friendly | Nylon complies with RoHS | No heavy metal pollution | No special requirements |
Selection suggestions:
High sealing requirements: electroplated zinc flange nut, with gasket to enhance sealing;
High corrosion environment: color-plated zinc nut, chromium-free passivation process is preferred;
Vibration environment: anti-loosening nut, all-metal type is suitable for high temperature scenes;
High temperature and high load: high-strength blackened nut, matched with 10.9 grade bolts;
Permanent connection: welding nut, projection welding or spot welding type is selected according to the process.
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