Shantou Xinqing Precision Machinery Technology Co.,Ltd

The material selection of cans should take into account sealing, pressure resistance, cost, environmental friendliness, and product adaptability (such as whether they come into contact with food or require high-temperature sterilization). Currently, the mainstream materials are mainly metal, which can be divided into two categories: aluminum and aluminum alloys, and tinplate (tin plated steel plate). In addition, there are also a small number of composite materials used in special scenarios. Different materials have significant differences in performance, cost, and applicable scenarios. The specific classification and characteristics are as follows:

1. Aluminum and aluminum alloys: the mainstream choice for lightweight and high recyclability

Aluminum and aluminum alloys are currently the most important materials for cans (especially beverage cans) worldwide, accounting for over 70%. Their core advantages lie in lightweight, easy processing, and high recyclability, making them perfect for high-frequency consumer categories such as carbonated beverages, beer, and functional drinks.

• Core material type

  Aluminum used for cans is mostly 3000 series aluminum alloys (such as 3004 and 3104 aluminum alloys), which use aluminum as the substrate and add elements such as manganese (Mn) and magnesium (Mg) to balance strength and ductility

• Manganese element: enhances the corrosion resistance of the alloy (avoiding acidic substances in beverages from corroding the can wall) and processing stability, ensuring that it is not easily cracked during can making;

• Magnesium element: enhances the strength of the alloy (to meet the pressure resistance requirements of easy to pull cans, such as withstanding internal pressure of 2-3 bar for carbonated beverages), while maintaining good tensile performance (aluminum coils can be stretched into the can body at once by punching, reducing welding processes).

  In actual production, the material of aluminum cans is mostly in the form of "aluminum coils" (thickness 0.2-0.3mm), which are made into seamless cans through processes such as "stretching thinning stretching edge rolling", without the need for welding, and have stronger sealing properties.

• Core performance advantages

• Ultimate lightweighting: The density of aluminum is only 2.7g/cm ³, far lower than steel (7.85g/cm ³), and the weight of aluminum cans with the same capacity (such as 330ml) is only 15-20g, which is 1/2 of a tin can and 1/10 of a glass bottle, greatly reducing logistics transportation costs (such as aluminum cans carrying more than 40% more than Makou iron cans during vehicle transportation), and also more suitable for portable scenarios (such as outdoor and sports).

• High ductility and ease of processing: 3000 series aluminum alloy has excellent ductility and can reduce the thickness of the can wall from the initial 0.25mm to below 0.1mm through the "thinning and stretching process" (the can bottom and can mouth are slightly thicker due to load-bearing needs), achieving "reduced design". At the same time, the scrap rate during processing is low (only 2% -3%), making it suitable for large-scale automated production (600-1200 cans can be produced per minute).

• Strong corrosion resistance and safety: A dense oxide film (Al ₂ O3) naturally forms on the surface of aluminum, which can isolate air, moisture, and acidic substances in beverages (such as phosphoric acid in cola and citric acid in fruit juice), avoiding tank wall corrosion; Some high-end aluminum cans will also be coated with food grade epoxy resin coating (thickness 2-5 μ m) on the inner wall to further prevent metal ion migration and ensure food safety (in accordance with the requirements of GB 4806.9 "National Food Safety Standard for Metal Materials and Products in Contact with Food").

• Extremely high recycling value: Aluminum can be infinitely recycled, and the recycling energy consumption is only 5% of primary aluminum (primary aluminum production requires electrolysis, which consumes a lot of energy; recycled aluminum only needs to be melted, which greatly reduces energy consumption). The global average recycling rate of aluminum cans exceeds 70% (some countries such as Japan and Germany reach over 90%). After recycling, it can be quickly converted into new aluminum coils with a short cycle time (only 1-2 months), and its environmental friendliness far exceeds that of materials such as plastic and glass.

• Applicable scenarios

  Mainly used for beverage cans, especially:

• Gas containing beverages, such as carbonated drinks (cola, Sprite), beer, and aluminum cans, have pressure resistance and sealing properties that can lock in gas and prevent leakage;

• Room temperature beverages, such as functional drinks, tea drinks, and fruit juice drinks, are lightweight and portable in line with consumer habits;

• Small capacity scenarios: such as 200ml and 330ml mini cans, the thin-walled design of aluminum cans can reduce the cost of a single can and adapt to the trend of "small portion" consumption.

2. Tinplate: Traditional choice for high strength and high temperature resistance

Tinplate (officially known as "tin plated steel plate") is one of the earliest materials used for cans. Its core components are low-carbon steel plate (substrate) and surface tin plating layer. With its high strength, high temperature resistance, and easy printing characteristics, it is still an important choice for food cans and some beverage cans, accounting for 20% -25% of the total material of cans.

• Core Material Structure

  The structure of tinplate is a "three-layer composite":

• Substrate: Low carbon steel plate (carbon content ≤ 0.15%), providing high strength and rigidity, ensuring that the tank body can withstand high temperature sterilization pressure (such as 121 ℃ high-pressure sterilization) and is not easily deformed;

• Tin plating layer: The surface of the steel plate is electroplated with pure tin (thickness 2-10 μ m), which is divided into two processes: "hot-dip tin plating" and "electroplating tin plating" (currently the mainstream is electroplating tin, with a more uniform coating). The tin layer can isolate the steel plate from food, prevent iron ion migration, and improve corrosion resistance and welding performance;

• Coating: The inner wall is usually sprayed with food grade phenolic resin or epoxy resin coating (thickness 3-8 μ m) to avoid the tin layer reacting with acidic or alkaline foods; The outer wall can be sprayed with printing coatings (such as offset ink), suitable for complex pattern designs.

  The processing technology of tinplate cans is different from that of aluminum cans: the can body is mostly "welded" (steel plates are rolled into cylinders and welded together by resistance welding), and the bottom and lid of the can are separately stamped and sealed with the rolled edges of the can body, so there are "welds" (strict testing of sealing is required to avoid leakage).

• Core performance advantages

• Ultra high strength and rigidity: The tensile strength of low-carbon steel plate can reach 300-500MPa, far higher than that of aluminum alloy (200-300MPa). The compression and impact resistance of tinplate cans are stronger, suitable for stacking and storage (can stack up to 3-5 meters high, aluminum cans can only stack 1-2 meters), and can also withstand pressure changes during high-temperature sterilization (such as when meat cans are sterilized at 121 ℃, the pressure inside the cans can reach 1.5 bar, and tinplate cans are not easily swollen or deformed).

• Excellent high temperature resistance: The melting point of tinplate (about 1538 ℃) is much higher than that of aluminum (660 ℃), and it can withstand high-pressure sterilization above 121 ℃ (aluminum cans can usually only withstand pasteurization below 100 ℃, and are prone to softening and deformation above 120 ℃), making it the only choice for high-temperature sterilized food cans (such as canned meat, canned fish, canned beans).

• Strong printing adaptability: The surface of the tinplate is smooth and flat, and the tin plating layer has good glossiness. It can be adapted to various printing processes such as offset printing, screen printing, hot stamping, and relief printing. The printed patterns have bright colors and strong adhesion (wear-resistant and not easy to fade), making it suitable for products that require long-term storage or emphasize appearance texture (such as gift cans and high-end nut cans).

• High cost stability: The raw material supply of low-carbon steel is stable (with sufficient global steel production capacity), and the price fluctuation is smaller than that of aluminum (which is more affected by the international commodity market). Therefore, the cost of tinplate cans is more stable, suitable for food enterprises with high cost sensitivity and long production cycles.

• Applicable scenarios

  Mainly used for food cans and some special beverage cans:

• High temperature sterilized food: for example, canned meat (lunch meat, Braised pork belly), canned aquatic products (tuna, sardine), canned fruits and vegetables (yellow peach, pea), they need to withstand 121 ℃ high pressure sterilization, and the high temperature resistance of tinplate cannot be replaced;

• Solid food at room temperature: such as nuts, cookies, chocolate. The rigidity of tinplate can protect the food from compression, and the sealing can prevent moisture and oxidation, extending the shelf life;

• Partial beverages: such as ambient temperature coffee, energy drinks (requiring long-term storage and rigidity of the can body), or beverage cans in regional markets (such as some developing countries where the cost advantage of tinplate is more obvious).

3. Special composite materials: a supplementary choice for niche scenes

In addition to pure metal materials, there are also a small number of cans that use a composite structure of "metal+other materials", mainly for special functional needs, accounting for less than 5%. Common types include:

• Aluminum plastic composite tank

  The structure consists of "aluminum foil+plastic layer" (such as outer PET plastic, middle aluminum foil, inner PE plastic), and the can body is made by composite technology. The can lid is made of aluminum pull ring. The core advantages are lighter weight, lower cost (10% -15% lower than pure aluminum cans), and strong barrier properties (aluminum foil can isolate light and oxygen); However, the disadvantage is that the strength is low (no pressure, easy to deform), and it is only applicable to non gas containing, low pressure products, such as powder drinks (milk tea powder, protein powder), small skin care products (hand cream, lipstick).

• Tin aluminum composite can

  The structure consists of a "can body made of tinplate and a can lid made of aluminum". Combining the high strength of tinplate with the ease of opening of the aluminum lid, it is mainly used for large capacity food cans (such as nut cans and miscellaneous grain cans weighing over 500g). The can body is made of tinplate to ensure rigidity and sealing, and the can lid is made of aluminum pull rings to enhance ease of opening (avoiding difficulties in opening the tinplate lid).

4. Core differences in mainstream materials (aluminum vs tinplate)

Starting from practical application scenarios and performance requirements, the core differences between aluminum and aluminum alloy cans and tin cans can be summarized as follows:

• In terms of weight, aluminum cans are lighter (about 15-20g for 330ml cans), while tin cans are heavier (about 30-35g for 330ml cans). Aluminum cans have significant advantages in logistics costs and portability;

• In terms of processing technology: aluminum cans are formed by seamless stretching (without welds, with stronger sealing), while tin cans are formed by welding (with welds, with a focus on testing sealing);

• In terms of pressure resistance and high temperature resistance: aluminum cans have moderate pressure resistance (can withstand 2-3bar, suitable for carbonated beverages) and low high temperature resistance (≤ 100 ℃, can only be pasteurized); Makou iron cans have higher pressure resistance (able to withstand 3-4 bar) and high temperature resistance (≤ 121 ℃, can be sterilized under high pressure), making them more suitable for high-temperature sterilized foods;

• In terms of recyclability, both have high recycling value. Aluminum cans can be infinitely recycled and have lower recycling energy consumption (recycling rate of 70%+), while tinplate has a slightly higher recycling rate (85%+) but higher recycling energy consumption than aluminum;

• In terms of cost and compatible products: aluminum cans have slightly higher costs and are greatly affected by fluctuations in aluminum prices, with core compatibility for beverage products; The cost of tinplate is more stable, and its core is suitable for high-temperature sterilized food and solid food.