Advantages and Types of Metal Cans in Food Packaging

Metal cans have been at the heart of food preservation for over two centuries. Whether it’s a tin of sardines on a supermarket shelf or a can of tuna packed for export, metal containers remain the go-to choice for packaging perishable food products – especially fish and seafood. Their ability to create a hermetically sealed, airtight environment makes them exceptionally effective at extending shelf life, retaining nutritional value, and protecting contents from light, moisture, and oxygen. But not all metal cans are the same. The three main types – tinplate, aluminum, and tin free steel (TFS) – each bring distinct properties to the table. Let’s break them down.

Why metal cans dominate food packaging 🔗

Metal cans offer a combination of strength, barrier protection, and thermal tolerance that few other packaging materials can match. According to a review published in the Journal of Food Science and Technology, metal-based packaging materials provide excellent barrier properties against gases, light, and moisture, making them widely used across the food industry. Round cans alone account for roughly 90% of the total metal can market.

For fish and seafood products specifically, metal cans are ideal because they can withstand the high temperatures needed for commercial sterilization (retort processing). During this process, canned fish is heated to temperatures exceeding 121°C, which destroys harmful microorganisms like Clostridium botulinum while maintaining a vacuum seal that keeps the product safe for years. Metal’s high thermal conductivity also ensures uniform heat distribution throughout the product, minimizing the risk of uneven sterilization.

Beyond safety, metal cans don’t require refrigeration during storage or transport. As noted on Wikipedia’s steel cans page, steel and aluminum packaging provide complete protection against light, water, and air, making them among the most tamper-evident of all packaging types. Food and beverages packed in steel cans retain vitamin content comparable to freshly prepared items – without any preserving agents. This ambient storage capability simplifies logistics, reduces energy costs, and makes canned fish accessible in regions far from coastlines.

Tinplate cans: the industry backbone 🔗

Tinplate cans are the most traditional and widely used type of metal can for food packaging. They consist of a low-carbon steel base coated with a thin layer of tin, applied through an electroplating process. The tin layer typically ranges from 2.8 to 11.2 grams per square meter and serves as a protective barrier between the steel and the food contents.

How tinplate is made 🔗

The manufacturing process starts with cold-rolled steel sheets (known as black plate), which are then passed through an electrolytic tinning line. The steel sheets travel through a bath of tin electrolyte, where a controlled electric current deposits a uniform layer of tin on both sides. After plating, the coated steel undergoes a flow-melting process – the tin is briefly melted to create a smooth, bright finish and form a tin-iron alloy layer at the interface. This alloy layer enhances the bond between the tin and steel, improving overall corrosion resistance.

Key properties of tinplate 🔗

Tinplate brings several properties that make it the preferred material for canning fish and other food products:

Corrosion resistance – The tin coating acts as a sacrificial anode in acidic conditions, protecting the steel base from rust. For mildly acidic foods (pH 2.5-7.5), the tin layer prevents hydrogen evolution and protects against internal corrosion. As noted by IspatGuru, tinplate’s protective ability is especially important for products in direct contact with acidic contents.

Heat resistance – Tinplate can comfortably withstand retort processing temperatures above 121°C, making it essential for commercially sterile fish products. This thermal stability ensures that cans maintain their structural integrity through repeated heating and cooling cycles.

Weldability and formability – Tinplate can be easily soldered and welded, which is critical for producing three-piece cans (body, top, and bottom). According to the Huaxiao Metal comparison, this excellent weldability makes tinplate essential for the integrity of traditional three-piece food cans.

Chemical compatibility – Tin is relatively inert when in contact with fish oils and proteins, which helps maintain the original taste and nutritional profile of canned seafood. For products like fruit juices, pale fruits, and fish in brine or oil, tinplate remains the standard choice.

Internal lacquers and coatings 🔗

Despite its corrosion resistance, tinplate is not entirely inert. For highly acidic or sulfur-containing foods (such as certain fish products), an additional internal lacquer or enamel coating is applied. These lacquers – typically epoxy-phenolic or vinyl-based resins – form a hard protective film on the metal surface. The coating prevents direct contact between the food and the tin, reducing the risk of metallic taste migration and discoloration. The Food Packaging Forum notes that tinplate’s reducing properties help prevent colour loss, flavour changes, and product oxidation in non-lacquered cans, but lacquering is still standard practice for most food applications.

Aluminum cans: lightweight and versatile 🔗

Aluminum cans have gained significant market share over the past few decades, especially for beverages and products where weight reduction and portability are priorities. While traditionally associated with soft drinks and beer, aluminum is increasingly used for certain fish and seafood products as well.

Material composition and manufacturing 🔗

Aluminum cans are typically made from aluminum alloys containing small amounts of manganese and magnesium for added strength. The manufacturing process for most modern aluminum cans uses a technique called drawing and wall ironing (DWI). A flat disc of aluminum is punched and drawn into a cup shape, then progressively ironed through a series of rings to thin the walls while maintaining the base thickness. This produces a seamless, one-piece can body (the two-piece can design) with walls as thin as 0.1 mm.

This seamless construction eliminates weak points like welded or soldered seams, reducing the risk of leakage and contamination. As Evergreen Resources explains, aluminum’s seamless one-piece structure is both strong and hygienic, allowing for precise shaping and advanced decoration.

Key properties of aluminum 🔗

Lightweight nature – Aluminum weighs roughly one-third as much as steel. This significantly lowers transportation and shipping costs. For large-scale fish processing operations that ship products globally, the weight savings translate directly into cost savings and a smaller carbon footprint during distribution.

Natural corrosion resistance – When exposed to air, aluminum forms a thin, stable oxide layer on its surface that acts as a natural barrier against further corrosion. This self-protecting property means aluminum cans require less additional coating compared to steel-based alternatives, though internal polymer linings are still commonly applied.

Excellent recyclability – Aluminum is one of the most recyclable materials in the world. It can be recycled infinitely without losing its properties, and recycling aluminum requires only about 5% of the energy needed to produce new aluminum from raw bauxite ore. This makes aluminum cans an environmentally favourable choice.

Good thermal conductivity – Aluminum conducts heat efficiently, which means canned beverages and food products chill quickly. However, for retort-processed fish products that require extended high-heat sterilization, tinplate generally performs better because it offers greater rigidity at sustained high temperatures.

Limitations for fish packaging 🔗

Despite its advantages, aluminum has some drawbacks for fish canning. It is softer and more prone to denting than steel, which can be a concern during rough handling and long-distance transport. Aluminum cans are also less suited to high-temperature retort processing compared to tinplate, making them more common for cold-fill or pressure-fill applications like carbonated beverages. For these reasons, aluminum is more frequently used for ready-to-eat, single-serve seafood products rather than traditional retort-processed fish.

Tin free steel (TFS) cans: the cost-effective alternative 🔗

Tin Free Steel – also called Electrolytic Chromium Coated Steel (ECCS) – was developed as an economical alternative to traditional tinplate. Instead of a tin coating, TFS uses a dual-layer chromium coating applied through electroplating, combining the structural strength of steel with specialised surface properties.

How TFS is produced 🔗

The production process begins with cold-rolled steel sheets (black plate), similar to tinplate manufacturing. These sheets are fed through an electrolytic coating line where they pass through a bath of chromic acid. This deposits two distinct layers on the steel surface: a thin layer of metallic chromium and an overlying layer of chromium oxide. After coating, the steel is given a light oil film to protect against humidity-related corrosion and to assist with handling during can fabrication.

According to IspatGuru’s technical overview, the combined thickness of the metallic chromium and chromium oxide layers is approximately 0.02 micrometres – far thinner than a typical tin coating. TFS is produced with metallic chromium coating weights ranging from 30 to 150 mg/sq m and chromium oxide coating weights from 5 to 35 mg/sq m.

Key properties of TFS 🔗

Excellent lacquer adhesion – TFS outperforms tinplate when it comes to paint and lacquer adhesion. The chromium oxide surface provides a superior bonding substrate for inks, varnishes, and protective coatings. This makes TFS popular for decorative cans and applications requiring high-quality printed finishes.

Sulphide resistance – This is a major advantage for fish canning. Protein-rich foods like fish release sulphur compounds during thermal processing, which can react with tin to form black sulphide stains inside the can. The metallic chromium in TFS has inherent sulphide resistance, which means it can pack protein-rich seafood without requiring expensive sulphur-resistant lacquers that tinplate would need.

Cost-effectiveness – Since chromium is significantly cheaper than tin, TFS offers meaningful cost savings over tinplate while maintaining reliable performance. The Huaxiao Metal comparison highlights that this raw material cost difference makes TFS a highly economical alternative for suitable applications, including can ends, closures, and crown caps.

Corrosion resistance (with coating) – While TFS provides good corrosion resistance after lacquering, it does not offer the same sacrificial protection that tin provides in an uncoated state. TFS must always be lacquered on both sides before use in food contact applications. In acidic environments, the absence of a sacrificial tin layer makes uncoated TFS more susceptible to corrosion.

Limitations of TFS 🔗

The most significant limitation of TFS is its poor weldability. The chromium oxide layer interferes with electrical current and heat transfer during welding, which means TFS cannot be used for traditional three-piece welded cans. Instead, TFS components are joined using adhesives or mechanical methods, or used in two-piece drawn can designs. This restricts its applications compared to tinplate. As the Journal of Food Science and Technology review notes, the need to remove coatings before welding hinders TFS’s extensive use for single-use containers.

TFS is also more sensitive to handling and storage conditions. It should be stored carefully to avoid humidity damage and ideally used within 10 days of unwrapping.

Comparing the three types of metal cans 🔗

Choosing between tinplate, aluminum, and TFS depends on the specific product, processing requirements, and budget. Here is a quick comparison of the key attributes:

Tinplate is best suited for products requiring high-temperature retort processing, strong structural integrity, and reliable corrosion protection in acidic environments. It remains the standard choice for canned fish like tuna, sardines, and mackerel.

Aluminum works best when lightweight packaging, portability, and premium aesthetics are priorities. It dominates the beverage sector and is increasingly used for single-serve, ready-to-eat seafood products.

TFS offers an excellent middle ground for applications where cost savings matter and welding is not required. Its superior sulphide resistance makes it particularly well-suited for fish can ends and closures, crown caps, and two-piece drawn cans for seafood.

Advantages of metal cans over other packaging materials 🔗

Regardless of the specific type, all metal cans share several inherent advantages that make them superior to alternatives like glass, plastic, or flexible pouches for many food applications:

Hermetic sealing – Metal cans create a completely airtight seal that prevents oxygen, moisture, and microorganisms from reaching the food. This is essential for maintaining commercial sterility in canned fish products.

Extended shelf life – Properly canned fish products can maintain quality and safety for 2 to 5 years at ambient temperature, without any need for refrigeration or preservatives. This dramatically reduces food waste and simplifies distribution logistics.

Tamper evidence – Metal cans show clear signs of tampering through visible dents, swelling, or broken seals, providing consumers with confidence about product safety.

100% recyclability – Both steel and aluminum cans are fully recyclable and can be recycled repeatedly without losing material quality. Globally, around 65% of steel cans are recycled, and aluminum has one of the highest recycling rates among packaging materials.

High-speed production compatibility – Metal cans work efficiently on automated filling and seaming lines. A tinplate production line, for instance, can produce hundreds of cans per minute, making metal packaging cost-effective at scale.

Limitations to keep in mind 🔗

Metal cans are not without drawbacks. They are heavier than plastic or flexible packaging, which increases transportation costs per unit. They are also rigid and inflexible, limiting the shapes and sizes available compared to pouches or plastic containers. Internal coatings must be carefully matched to the product type to prevent issues like metallic taste migration or BPA-related concerns from epoxy linings – though BPA-free (BPA-NI) coatings are becoming increasingly standard across the industry.

There is also the risk of internal corrosion if the wrong can type or coating is selected for a particular food product. For example, using uncoated TFS for highly acidic fish products could lead to rapid corrosion, while insufficiently coated tinplate may cause sulphide blackening in protein-rich seafood.

The role of metal cans in sustainable packaging 🔗

Sustainability is becoming a major factor in packaging decisions. Metal cans score well on this front. Both steel and aluminum are among the most recycled materials on the planet, and recycling metal saves significant energy compared to primary production. The metal packaging industry has also been working on lightweighting – reducing the amount of material used per can through advanced manufacturing techniques like DWI, while maintaining structural integrity. This reduces raw material consumption, transportation emissions, and overall environmental impact.

What do you think? Given the trade-offs between tinplate, aluminum, and TFS cans, which type do you think will see the most growth in the fish packaging industry over the next decade? How might evolving sustainability standards influence the choice of metal can type for seafood products?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC7270472/
2. https://en.wikipedia.org/wiki/Steel_and_tin_cans
3. https://www.ispatguru.com/tin-free-steel/
4. https://www.huaxiaometal.com/blogs/tinplate-vs-electrolytic-tin-free-steel-whats-the-difference.html
5. https://foodpackagingforum.org/resources/background-articles/food-packaging-materials/metal
6. https://evergreenresources.com/food-can-format-overview/