14/10/2025
The material used to make cans determines their purpose, cost, and performance.
Main material types:
👉Tinplate: This is the common name for tin plated steel sheet. It is the most traditional material for food and beverage cans. It is actually coated with a layer of pure tin on a low-carbon steel sheet. Tin has the functions of rust prevention, corrosion prevention (especially for acidic contents), and aesthetics.
👉Aluminum: mainly used for two-piece cans (such as cola cans, beer cans). The advantages are light weight, good ductility, easy molding, and good surface treatment effect.
👉TFS: Chrome plated iron, also known as Wuxi steel plate. It uses a metal chromium layer instead of a tin layer, which is lower in cost but slightly less corrosion-resistant. It is mainly used for can bottoms, lids (bottom lids), and some food cans with low corrosion requirements.
💋Key points of material performance:
Corrosion resistance: The material must be able to resist the corrosion of its contents, especially acidic and salty foods.
Mechanical strength: The tank body should be able to withstand the pressure during processing, transportation, and stacking, as well as the vacuum or pressure inside the tank.
Welding/bonding performance: For three piece cans, the can body needs to be welded or bonded, and the material must be suitable for these processes.
2、 Can Structure and Manufacturing Process
This is the basis for distinguishing different tank types.
Three major can types:
👉Three piece can: composed of a can body, a can bottom, and a can lid. Traditional food cans, such as lunch meat cans and milk powder cans, often have this structure. The can body has seams (welded or bonded), which are then connected to the bottom and lid of the can by rolling and sealing.
👉Two piece can: consisting of a single body with a bottom and a lid. Through the "punching, pulling, and stretching" process, it is formed as a whole without side seams and has better sealing performance. This structure is commonly used for beverage cans.
👉Easy to open lid: This is not a can type, but a key can lid technology. There is a pre pressed tear line on the lid, which can be opened through a pull tab. This is a standard configuration for modern beverage and food cans.
💋Key process terms:
Sealing: The process of firmly closing the can body and lid is the core link to ensure sealing.
Internal coating: Apply a layer of organic coating (such as epoxy resin) on the inner wall of the metal can to prevent direct contact between the contents and the metal, and to avoid chemical reactions and leaching of metal ions.
External printing: The printing decoration on the outside of the tank.
3、 Quality and Performance (Very Critical!)
This is a hard indicator to measure the quality of a jar.
Sealing: This is the lifeline. Any leakage can lead to product spoilage. 100% inspection through leak detection equipment.
Pressure resistance/vacuum degree: For carbonated beverage cans, they need to be able to withstand internal pressure without deformation; For food cans, after vacuuming, they need to be able to resist atmospheric pressure without sinking.
Coating integrity: The inner coating must be intact and undamaged, otherwise it may corrode the tank. Impedance testing is commonly used for detection.
Opening force: For easy to open lids, the force required to open the pull tab should be moderate, ensuring that it will not accidentally open during transportation and allowing consumers to easily open it.
4、 Common Defects and Problems
Know what an unqualified jar is.
Swelling of the can: The bulging of the bottom and lid of the can is usually caused by microbial decay or chemical corrosion, and is a serious quality problem.
Iron sulfide: Protein rich foods (such as meat and corn) react with tinplate to produce black iron sulfide spots on the inner wall of the can, which affect appearance but are usually non-toxic.
Hydrogen swelling: The electrochemical reaction between acidic contents and the tank produces hydrogen gas, leading to tank swelling.
Scratch/Scratch: Physical damage to coatings or printing during production or transportation, affecting appearance and corrosion resistance.
Edge defect: The sealing is not tight enough, resulting in seal failure.
5、 Downstream Applications and Customer Requirements
Jars are designed to serve the contents and must understand the needs of customers.
Content adaptability:
Acidic foods (fruits, tomato sauce): require materials with strong acid and corrosion resistance and inner coating.
Carbonated beverages (cola, beer): Two piece cans that require high pressure resistance.
Aquatic products and meat: require the use of sulfur resistant coatings (to prevent the production of iron sulfide).
Shelf life requirements: Different foods have different requirements for oxygen and light barrier properties, which affects material selection and coating design.
Filling process: The canning factory needs to understand the customer's filling line speed and sterilization conditions (pasteurization or high temperature and high pressure sterilization) to ensure that the cans are compatible with these subsequent processes.
6、 Industry Trends and Norms
Sustainable development: Lightweight (reducing material usage), using recycled materials, and improving recyclability are currently the most important trends.
Regulations and Safety: It is necessary to be familiar with food safety regulations (such as China's GB standards, EU's EC No 1935/2004, etc.) to ensure that the internal coating materials, inks, etc. meet the requirements of food contact materials.
