Why Is Adhesive Applied to Screws?

Applying adhesive to screws (usually referring to thread-locking adhesive) primarily aims to prevent screws from loosening or falling off under conditions such as vibration, impact, and temperature changes, thereby ensuring the stability and safety of mechanical structures, electronic devices, or components. Below are the specific reasons and application scenarios:

1. Anti-Loosening: Counteracting Vibration and Dynamic Loads

Vibration Environments: In fields such as automobiles, motorcycles, industrial equipment, and aerospace, screws may gradually loosen due to vibration. Thread-locking adhesives can fill thread gaps and fix screws through chemical bonding, preventing spontaneous loosening caused by vibration (e.g., engine components, chassis screws).
Dynamic Loads: In components subject to frequent stress or movement (e.g., motors, pump equipment), screws may loosen due to repeated force if not secured. Adhesive application significantly improves connection reliability.

2. Anti-Corrosion and Sealing: Protecting Threads and Isolating Environments

Anti-Corrosion: Metal screws are prone to rust in humid, acid-alkaline, or other corrosive environments. Thread adhesives form an isolation layer, preventing moisture, oxygen, or chemicals from contacting threads and extending screw lifespan (e.g., outdoor equipment, bathroom hardware).
Sealing Function: Some thread adhesives are sealant, which can prevent gas or liquid leakage through thread gaps (e.g., screws in pipe connections, hydraulic systems).

3. Positioning and Fixing: Ensuring Assembly Accuracy

Pre-Positioning: In precision equipment (e.g., electronic instruments, precision machinery), screws must be fixed in specific positions to ensure assembly accuracy. Adhesive application prevents screws from shifting during installation or affecting functionality due to micro-displacement during long-term use (e.g., fixing circuit board components, connecting optical instrument parts).
Anti-Misoperation: For screws that should not be disassembled arbitrarily (e.g., safety devices, anti-tampering components), adhesive application serves as identification and fixation, avoiding hidden dangers caused by unauthorized disassembly by non-professionals.

4. Targeted Functions of Different Adhesive Types

Thread-locking adhesives are categorized into various types based on strength and purpose to meet diverse scenario requirements:

Type	Characteristics	Typical Applications
Low-Strength Adhesive	Easy to disassemble; used for screws requiring frequent maintenance (e.g., electronic device housing screws).	Laptops, household appliances
Medium-Strength Adhesive	Moderate bonding force; detachable with tool assistance; suitable for general mechanical components.	Automotive interior parts, office equipment
High-Strength Adhesive	Strong bonding force; requires heating (e.g., high temperature) for disassembly; used for permanently fixed key components.	Engine bolts, heavy machinery connections
High-Temperature Resistant Adhesive	Withstands high-temperature environments (e.g., above 200°C); suitable for screws in high-temperature areas such as engines and exhaust systems.	Automobile engines, industrial high-temperature equipment
Fast-Curing Adhesive	Rapid curing; suitable for emergency repairs or scenarios requiring quick assembly.	Temporary repairs, assembly line production

5. Advantages Over Traditional Anti-Loosening Methods

Compared to other anti-loosening methods (e.g., spring washers, lock washers, welding), adhesive application offers the following advantages:

Low Cost: No additional mechanical parts (e.g., washers) required, simplifying the assembly process.
Wide Applicability: Suitable for various thread specifications (metric, imperial) and materials (metal, plastic).
Excellent Sealing: Simultaneously solves loosening and leakage issues.
No Bulky Structures: Ideal for compact spaces or scenarios with appearance requirements (e.g., consumer electronics, medical devices).

Notes

Select Appropriate Adhesive Type: Choose thread adhesives with corresponding strength and characteristics based on screw size, material, and working environment (temperature, humidity, load).
Proper Operation: Ensure threads are clean and dry; apply an appropriate amount of adhesive (excess may overflow and contaminate components, while insufficient amounts reduce anti-loosening effectiveness).
Curing Time: Most thread adhesives require a certain curing time (typically 30 minutes to 24 hours); avoid severe vibration or stress before full curing.

Why Is Adhesive Applied to Screws?