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The potential safety hazards caused by corrosion in crane hooks are a serious concern. Corrosion not only weakens the hook's structural strength but can also cause sudden fractures, leading to serious accidents. The following is a detailed analysis of the impact of corrosion on hook safety, common corrosion types, and preventive measures:

1. The harm of corrosion to the safety of hooks

1. Decreased material strength

   • Corrosion will cause the effective cross-sectional area of the metal to decrease. For example, if the hook neck is corroded by 1mm, its load-bearing capacity may drop by 10% to 15%.

   • Case : Due to corrosion from marine salt spray, the hook thickness of a port was reduced from 50mm to 42mm (exceeding the 10% scrap standard), and it broke during lifting.

2. Increased stress concentration

   • Defects such as corrosion pits and pitting can become crack initiation points, accelerating fatigue growth under dynamic loads.

   • Data : Hook fatigue life in a corrosive environment can be shortened to 30% of normal operating conditions.

3. Risk of sudden failure

   • Hidden corrosion, such as rust at the root of threads, may go undetected, leading to joint failure.

2. Common corrosion types and scenarios

III. Key preventive measures

1.  Material selection

• High corrosion resistance alloy :

  • 316 stainless steel (marine environment), monel alloy (acid resistant).

• Surface treatment :

  • Hot-dip galvanizing (thickness ≥80μm), Dacromet coating (salt spray resistance 1000h).

2.  Protection technology

• Active protection :

  • Cathodic protection : installation of sacrificial anodes (such as zinc blocks, suitable for offshore platforms).

  • Corrosion Inhibitor : Spray volatile corrosion inhibitor (VCI) regularly.

• Passive protection :

  • Epoxy coal tar paint (buried part), polyurethane topcoat (UV protection).

3.  Inspection and maintenance

• Inspection frequency :

  Environmental corrosiveness	Inspection cycle	Key areas
  Mild (indoor dry)	6 months	Hook, thread
  Moderate (wet outdoors)	3 months	Hook neck and bearing seal
  Heavy (Chemical/Marine)	per month	Full surface + non-destructive testing

• Detection method :

  • Ultrasonic thickness measurement (corrosion residual thickness).

  • Penetrant testing (PT) (to detect pitting).

4.  Usage Guidelines

• Cleaning requirements :

  • After lifting corrosive substances (such as salt and acid), rinse with fresh water and dry.

• Storage conditions :

  • The humidity in the warehouse should be less than 60%, or the goods should be sealed and stored after applying anti-rust grease (such as Castrol Rustilo).

4. Scrap standards for corroded hooks

1. Size Standard :

   • The corrosion thinning of the load-bearing parts such as the hook mouth and hook neck is greater than 10% of the original thickness (GB 6067.1).

2. Defect criteria :

   • Pitting depth > 2 mm or dense pitting (spacing < 5 times the pore diameter).

3. Strength standards :

   • The deformation in the static load test exceeded the standard (permanent deformation under 1.25 times the load > 0.5%).

5. Industry-specific solutions

VI. Typical Case Analysis

Case 1: Shipyard hook breakage accident

• Cause : Hidden pitting (3mm deep) on the hook neck was not detected, and the fatigue crack expanded to a critical size.

• Lesson : Introduce portable endoscopes to inspect hidden parts such as threads.

Case 2: Brittle fracture of a hook in a chemical plant

• Cause : Stress corrosion cracking (medium: H₂S, material: 42CrMo without dehydrogenation treatment).

• Improvement : Use sulfur-resistant steel (such as AISI 4130) and strictly control the heat treatment process.

7. Future Technology Directions

1. Intelligent monitoring :

   • Corrosion rate sensors (such as electrochemical impedance spectroscopy probes) transmit data to the cloud platform in real time.

2. Self-healing coatings :

   • Microencapsulated corrosion inhibitor (automatically releases and repairs after scratches, laboratory stage).

Summarize

Corrosion is the "invisible killer" of hooks and needs to be addressed through a three-in-one strategy of "materials-protection-monitoring" :

• High-risk environment : choose special materials + multiple protections.

• Daily management : Strictly implement the "clean-check-record" process.

• Technology upgrade : Promote the popularization of intelligent corrosion monitoring systems.

Warning :

“Rust is not a decoration, but a countdown to an accident!”
- If signs of corrosion are found, they must be evaluated immediately and it is strictly forbidden to operate with “diseases”!