In the production of ROPP (Roll-On Pilfer-Proof) bottle caps, the selection of aluminum alloy must take into account deep-drawing performance, corrosion resistance, cost-efficiency, and food safety compliance.

Currently, the most commonly used aluminum alloys for ROPP caps in the market include the following:

1. Primary Choice: 8011 Aluminum Alloy

8011 aluminum alloy offers excellent formability, high earing resistance, and flatness, making it particularly suitable for deep-drawing processes. It is widely used for wine bottle caps and other beverage closures.

(1) Key Advantages

a. Superior Deep-Drawing Properties
8011 deep-drawing aluminum sheet features excellent ductility and plasticity, meeting the demands of ROPP caps for deep drawing and curl-forming. It ensures smooth processing on high-speed production lines and reduces earing, improving material utilization.

b. High Cost Efficiency
As the most widely used cap alloy, it has low raw material cost and a well-established supply chain.

c. Surface Compatibility
Easily compatible with chromate treatment, lacquering, or printing, making it suitable for custom branding (e.g., silk screen printing, embossing).

d. Moderate Strength
Provides adequate mechanical strength to maintain cap integrity and sealing performance.

(2) Typical Applications

Used in wine, pharmaceutical, and standard beverage bottle caps, such as 30×60mm and 28×15mm sizes.

(3) Mechanical Properties

2. High-Performance Alternative: 3105 Aluminum Alloy

3105 aluminum closure sheet has medium strength and is commonly used for pressurized container lids.

(1) Key Advantages

a. Higher Strength
Compared to 8011, 3105 offers greater mechanical strength, making it more suitable for withstanding internal pressure.

b. Excellent Corrosion Resistance
Retains aluminum’s inherent corrosion resistance.

c. Good Formability and Weldability
Despite higher strength, it still offers good processability.

d. Stress-Crack Resistance
Especially critical for applications requiring internal pressure tolerance.

(2) Application Scenarios

Pressurized containers (e.g., carbonated drinks, sparkling liquids) that require higher tensile strength (175–225 MPa in H16 temper).

Corrosive environments: Magnesium content (0.2–0.8%) enhances oxide film stability and extends sealing life.

(3) Limitations

Slightly higher cost than 8011 and somewhat reduced deep-drawing extensibility (elongation 1–2%).

(4) Mechanical Properties

3. Alloys for Special Requirements: 5052 and 3003 Aluminum

• 5052 Alloy

Extreme Corrosion Resistance: Contains 2.2–2.8% magnesium, making it suitable for marine environments or high-salt contents (e.g., seafood seasoning).

High Strength: Tensile strength of 280–320 MPa (H18), but limited formability (elongation 2–3%).

• 3003 Alloy

Balanced Performance: Higher strength than 8011 (tensile strength 145–185 MPa), ideal for general-purpose caps requiring moderate reinforcement.

Purchasing Recommendations

ROPP caps typically require internal coating (e.g., epoxy varnish) to ensure sealing performance and compatibility with contents, along with external printing and decoration. The selected aluminum alloy must offer strong adhesion properties for coatings and be suitable for printing.

Prefer suppliers offering chromate pretreatment and DOS lubrication (e.g., MC Aluminum) to ensure high stamping yield. For bulk orders, request earing rate ≤3% in the quality inspection report.