I. Material is fundamental
Stainless steel: 316 is more corrosion-resistant than 304, suitable for marine and chemical environments.
Carbon steel: Sufficient for ordinary environments, but rust prevention treatment is necessary.
Alloy steel: The first choice for high-strength applications such as engines and high-pressure equipment.
II. Incorrect strength grade
8.8 grade: Sufficient for ordinary maintenance.
10.9 grade: Mainstay for bridges and heavy machinery.
12.9 grade: Ultra-high strength requirements such as aerospace.
III. Surface treatment matters
Zinc plating: Short-term rust prevention indoors.
Hot-dip galvanizing: More durable for long-term outdoor use.
Dacromet: Corrosion resistance is 7-10 times that of electro-galvanizing.
IV. Details determine success or failure
Thread: Fine threads are better for preventing loosening, coarse threads are easier to install and remove.
Process: Heat treatment must be standardized to avoid hydrogen embrittlement.
Matching: Nut grade must match bolt grade.
