1. Visual Inspection
Zinc Coating Condition:
Normal: The surface is a uniform dark gray color, with no peeling or white rust (zinc hydroxide corrosion products).
Replacement Required: Extensive white rust, reddish-brown rust (exposed base material), or flaking of the zinc coating occurs.
Threads and Head:
Check for wear, deformation, or stripping of the threads, and for skewness of the head (which affects tightening).
2. Functional Testing
Torque Test:
If the bolt cannot be tightened to the standard torque (e.g., grade 8.8 bolts must comply with GB/T 3098.1) or if the preload is insufficient, it should be replaced.
Length Measurement:
High-strength bolts (e.g., grade 10.9) should be scrapped if their elongation exceeds 2% of the original design length. 3. Environment and Service Life
Highly corrosive environments (such as coastal areas and chemical plants):
The zinc coating's lifespan is shortened to 10-15 years, requiring regular inspection and early replacement.
Normal environments:
Hot-dip galvanized bolts have a lifespan of approximately 20 years, but the integrity of the zinc coating should be inspected every five years.
