Galvanized bolts are primarily used in environments requiring moderate rust resistance but not extreme corrosion, such as outdoor infrastructure, construction and steel structures, power and telecommunications, vehicles and machinery, furniture, and home appliances.
Additionally, due to the differing friction coefficient of the zinc coating compared to standard bolts, precise preload is required during installation. Refer to the torque standards for galvanized bolts, as the values for plain bolts cannot be directly applied.
Comparison with Stainless Steel Bolts
| products |
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| Characteristics | Galvanized bolts (carbon steel + coating) | Stainless steel bolts (e.g., 304/316) |
| Rust Prevention | Sacrificial protection; loses effectiveness once coating is depleted | Base material is corrosion-resistant, providing overall rust resistance |
| Strength | High. Carbon steel substrates can achieve very high strength grades (e.g., 8.8, 10.9, 12.9) | Relatively low and prone to galling. The strength of 304/316 generally corresponds to or falls below Grade 8.8 |
| Low cost | High value for money | High |
| Applicable Environments | Atmospheric corrosion, rust prevention for a specified period | Highly corrosive environments, chemical corrosion, sanitary environments such as food processing and medical facilities |
Primary Galvanizing Processes and Their Characteristics
Electrogalvanizing
Electrolytic principle,Depositing a zinc layer on the bolt surface
Smooth and shiny surface, often with blue-white, multicolored, or silvery-white hues
Rust prevention capability is average, typically achieving 48-120 hours in neutral salt spray tests
For indoor, dry environments or equipment requiring aesthetic appeal
Hot-dip galvanizing
Immersing the bolt into molten zinc at approximately 450°C
Thick coating with a rough surface, featuring zinc nodules and crystalline patterns, appearing dull silver-gray
Exceptional corrosion resistance, with salt spray test endurance reaching hundreds to thousands of hours
For outdoor, highly corrosive environments
Mechanical galvanizing
At room temperature, mechanically impacting zinc powder onto the surface for "cold plating"
Uniform coating with a matte gray finish, free from hydrogen embrittlement issues
Controllable thickness (generally 20-80μm) and excellent corrosion resistance
Suitable for high-strength, fatigue-resistant components vulnerable to hydrogen embrittlemen
Dacromet/Zinc-chromate coating
Coating with zinc chromate solution followed by baking to form an inorganic coating
Matte silver-gray or silver-gray, with an extremely thin and uniform coating
Corrosion resistance significantly surpasses electrogalvanizing, achieving hundreds of hours in salt spray tests
Suitable for automotive, high-speed rail, and outdoor precision components
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