Full-category Comparison Of Fastener Surface Treatment, Selection & Purchasing Guide For Galvanized, Dacromet, Passivation & Blackening Process

p>Surface treatment determines the service life, appearance and corrosion resistance of fasteners in one-stop supporting procurement. Many purchasers only focus on price rather than process, resulting in outdoor equipment rusting, coating peeling, color difference and salt spray test failure. Fasteners of different materials and working conditions must match corresponding surface treatments to balance cost performance and reliability.

1. Parameter Comparison Of Mainstream Fastener Surface Treatments

Treatment Process	Applicable Material	Standard Salt Spray Hours	Wear Resistance	Appearance	Cost Level	Application Scenario
Electro-galvanizing	Carbon steel standard parts	24~72h	Average, easy coating peeling	Bright & rich colors	Very low	Indoor equipment, regular sheet metal, dry environment
Hot-dip Galvanizing	Large bolts & screw rods	300~500h	Excellent thick coating	Rough surface with zinc bumps	Medium	Outdoor steel structure, municipal equipment
Dacromet Coating	High-strength & precision parts	800~1200h	Good friction resistance	Matte silver gray, uniform texture	Medium-high	Wind power, PV, coastal high-corrosion equipment
Stainless Steel Passivation	SUS304/316 parts	500~1000h	Excellent, no coating peeling	Natural uniform metal color	Medium	Precision electronics, outdoor cabinets, high-end equipment
Steel Blackening	Small carbon steel parts	12~24h (oil sealed)	Poor, easy wear & exposure	Pure black matte delicate appearance	Very low	Indoor precision assembly & decorative fasteners

2. Accurate Selection Rules For One-stop Procurement

1. Indoor dry industrial control, home appliance and regular sheet metal: Electro-galvanizing with optimal cost performance; 2. Outdoor brackets and municipal steel structures: Hot-dip galvanizing with thick anti-corrosion coating; 3. New energy and coastal high-salt-fog projects: Dacromet or stainless steel passivation to avoid rust rework; 4. Precision structural and decorative parts: Blackening & oil sealing for delicate appearance and indoor rust prevention.

3. Common Purchasing Misunderstandings & Avoidance Tips

1. Ordinary electro-galvanizing for outdoor equipment: Inevitably rust in short term, upgrade to Dacromet or hot-dip galvanizing; 2. Hot-dip galvanizing for precision threads: Excess coating causes thread locking and gauge failure; 3. Omitted passivation for stainless steel parts: Residual iron ions lead to large-area flash rust; 4. Blackening parts without oil sealing: No anti-rust ability, easy oxidation and failure.