What Are Food Cans Made Of?

Content

1 What Materials Are Food Cans Made Of? The Direct Answer
2 The Three-Layer Structure of Can Body Steel
3 Tinplate vs. Tin-Free Steel vs. Aluminum: A Material Comparison
4 Three-Piece vs. Two-Piece Food Cans: How Can Body Steel Is Used Differently
- 4.1 Three-Piece Food Cans
- 4.2 Two-Piece Food Cans (DWI Process)
5 Why Low-Carbon Steel Is the Foundation of Can Body Steel
6 The Role of Tin Coating Thickness in Food Can Performance
7 Food Safety Requirements for Can Body Steel
8 Which Foods Are Packaged in Steel Food Cans?
9 Can Body Steel and Sustainability: The Recyclability Advantage

What Materials Are Food Cans Made Of? The Direct Answer

Food cans are made primarily from two materials: tinplate (tin-coated low-carbon steel) and aluminum. For the can body specifically, can body steel — electrolytic tinplate (SPTE) or tin-free steel (TFS) — is the dominant material worldwide. The steel provides structural rigidity and pressure resistance; the tin or chromium coating on its surface provides corrosion protection and food-safe contact properties. A food-grade internal polymer coating is then applied as a final barrier between the metal and the food product.

In short, what we call a "tin can" is not made of pure tin — it is a precisely engineered multi-layer structure in which low-carbon steel forms the structural core, with metallic and polymer coatings doing the protective work.

The Three-Layer Structure of Can Body Steel

Understanding why can body steel performs so well for food packaging requires looking at it as a layered system rather than a single material. Each layer has a specific engineering function:

Layer 1 — Low-Carbon Steel Base

The foundation of any food can body is a cold-rolled low-carbon steel sheet. This steel is processed into extremely thin, uniform coils through hot rolling followed by cold rolling, which aligns the grain structure to give it the combination of strength and ductility needed for can-making. It must be strong enough to withstand retort sterilization pressures and stackable load during shipping, yet ductile enough to be stamped, drawn, and formed without cracking.

Layer 2 — Tin or Chromium Coating

The steel base is electroplated with a protective metallic layer. In tinplate, this is commercially pure tin applied at a thickness of typically 0.4–1.5 μm. The tin layer prevents the steel from corroding when in contact with food, acts as a lubricant during the drawing process, and enables the electrical resistance welding used to form the side seam of three-piece cans. In tin-free steel (TFS), a chromium and chromium oxide layer replaces tin — thinner and lower in cost, but not weldable by standard methods, so it is typically used for can ends and lids rather than can bodies.

Layer 3 — Internal Polymer Coating

A food-grade organic coating — typically epoxy resin, polyester resin, or acrylic-based lacquer — is applied to the interior surface to create an inert barrier between the metal and the food. This coating is especially critical for acidic products (tomatoes, citrus juices, vinegars) and sulfur-rich vegetables (asparagus, garlic, onion) where direct metal-food contact would cause discoloration, off-flavors, or accelerated corrosion. All coating materials must pass food contact safety assessments under applicable regulations.

Tinplate vs. Tin-Free Steel vs. Aluminum: A Material Comparison

Three principal materials are used across the full range of food and beverage cans. Each is selected based on the product type, processing requirements, and manufacturing economics.

Comparison of the three primary food can materials by key performance criteria
Property	Tinplate (SPTE)	Tin-Free Steel (TFS)	Aluminum
Protective Coating	Tin (0.4–1.5 μm)	Chromium + Chromium Oxide	Natural Oxide Layer
Weldability	Excellent (resistance welding)	Poor (coating must be removed)	Not applicable (drawn & ironed)
Rigidity	High	High	Moderate
Heat Resistance	Excellent (retort-compatible)	Excellent	Good
Weight	Heavier	Heavier	Light (1/3 weight of steel)
Primary Can Use	Food can bodies (3-piece)	Can ends, lids, easy-open ends	Beverage cans (2-piece)
Recyclability	Fully recyclable	Fully recyclable	Fully recyclable

For food can bodies — vegetables, fruits, meats, seafood, sauces, and pet food — tinplate is the standard material because its weldability is essential for forming the side seam of three-piece cans, and its heat resistance suits retort sterilization processes that reach temperatures of 121°C or higher.

Three-Piece vs. Two-Piece Food Cans: How Can Body Steel Is Used Differently

The structure of a food can — whether three-piece or two-piece — determines exactly how can body steel is processed and what material properties are most critical.

Three-Piece Food Cans

The most widely used format in global food processing. The can consists of a cylindrical body (formed from a flat sheet of tinplate and welded at the side seam), plus two separate end pieces seamed on. This format offers maximum flexibility in height, diameter, and volume, making it suitable for the broadest range of food products. The side seam is formed by electrical resistance welding, which is why tinplate — with its tin layer facilitating the weld — is the preferred can body steel for this construction. Products packaged in three-piece tinplate cans include canned vegetables, tomato products, sauces, beans, fish, meat, and oils.

Two-Piece Food Cans (DWI Process)

In the drawn-and-wall-ironed (DWI) process, the can body and bottom are formed from a single flat disc of metal using a cupping press and a series of ring dies. The can wall is simultaneously thinned and elongated, creating a seamless one-piece body. This eliminates both the vertical side seam and the bottom seam — the areas most vulnerable to corrosion. The DWI process is widely used for beverage cans in aluminum, and is increasingly applied to food cans in tinplate where high production volumes of a single specification are required.

Why Low-Carbon Steel Is the Foundation of Can Body Steel

Not all steel is suitable for food can production. Can body steel must meet a demanding combination of mechanical, chemical, and dimensional requirements that only carefully controlled low-carbon steel grades can consistently deliver.

Low carbon content for ductility: Higher carbon content makes steel harder and less ductile. Can body steel uses low-carbon grades to ensure the sheet can be stamped, drawn, and formed without cracking or tearing during high-speed can-making operations.
Uniform thickness and flatness: Can body steel is cold-rolled to extremely tight thickness tolerances — typically in the range of 0.13–0.49 mm depending on the can format and application. Thickness variation across a coil directly affects can wall uniformity and the consistency of the welded seam.
Controlled temper (hardness) grades: Temper grades, typically designated T1 through T5 (or DR grades for double-reduced steel), define the hardness of the sheet. Softer grades suit deep-drawing applications; harder grades are used for lids and can ends where rigidity matters more than formability.
Clean surface finish: The surface must be free of oxides, scale, and contaminants before tinning, as any surface defect will cause non-uniform tin adhesion and potential corrosion weak points in the finished can.
Magnetic properties (for recycling): Unlike aluminum, steel is magnetic — a property that makes it straightforward to separate and recover from mixed waste streams using magnetic sorting equipment, supporting high recycling rates.

The Role of Tin Coating Thickness in Food Can Performance

The tin layer on electrolytic tinplate is not decorative — it is an active functional component with direct implications for food safety, processability, and shelf life. The tin coating weight is specified in grams per square meter (g/m²) and can differ between the inside and outside surfaces of the same sheet — a configuration known as differential coating.

Interior (heavier coating): The inside surface typically carries a heavier tin coating to provide maximum corrosion protection against the food product. For acidic foods, higher coating weights extend the protective life of the can.
Exterior (lighter coating): The outside surface can be coated more lightly since it faces the atmosphere rather than the food. Reducing the tin weight on the outside lowers material cost without compromising food safety.
Lubrication during forming: During the drawing and ironing process, the tin layer also serves as a lubricant between the steel and the forming dies, reducing friction and die wear and improving the surface quality of the finished can body.
Sacrificial protection mechanism: In the presence of food products that form a weak acid environment inside the can, tin acts as a sacrificial anode — dissolving preferentially to protect the underlying steel from corrosion. The amount of tin that dissolves during the shelf life of the can is regulated to be well within safe limits.

Food Safety Requirements for Can Body Steel

Because can body steel comes into direct or indirect contact with food, it is subject to rigorous food safety regulation in all major markets. The key requirements address metal migration, coating safety, and manufacturing process control.

Metal Migration Limits

Regulatory frameworks require that the migration of metal ions — particularly tin, iron, chromium, and heavy metals such as lead and nickel — from the can into food remain below prescribed limits. Laboratory migration testing simulates the food contact environment (acidic, alkaline, and oily) to verify compliance. Modern tinplate cans, with proper internal coatings, are designed to meet these limits across the full intended shelf life of the product.

Internal Coating Compliance

The organic coatings applied to the interior of food cans must themselves comply with food contact material regulations. Coating formulations — based on epoxy, polyester, or acrylic systems — undergo safety assessment to confirm that no substances migrating from the coating exceed the applicable specific migration limits (SML) or overall migration limits (OML) established by authorities such as the EU Commission Regulation on food contact materials or equivalent national standards.

Manufacturing Process Controls

During can body manufacturing, process controls prevent physical contamination (metal debris, welding residues) and ensure dimensional consistency of the weld seam and double seam at the can ends. High-speed vision inspection systems on modern can lines verify seam integrity at production rates of thousands of cans per minute.

Which Foods Are Packaged in Steel Food Cans?

Tinplate can body steel is the material of choice for any food product that undergoes retort sterilization — heating the sealed can to 121°C or above to eliminate bacterial contamination and achieve commercial sterility. The steel's heat resistance and structural rigidity are essential for withstanding the internal pressure generated during this process. Common applications include:

Vegetables and legumes: Tomatoes, sweetcorn, green beans, chickpeas, kidney beans — high-acid products especially benefit from tinplate's corrosion-resistant properties with appropriate internal coatings.
Fruit: Canned peaches, pineapple, mandarin segments, and fruit cocktail in syrup — tinned steel was historically the standard for fruit juices and pale canned fruits.
Meat and poultry: Canned beef, pork luncheon meat, chicken, and prepared meat products packaged for extended ambient shelf life.
Fish and seafood: Tuna, sardines, mackerel, salmon, crab, shrimp, and mussels — often packed in oil, brine, or sauce in polymer-coated tinplate or TFS cans, achieving shelf lives exceeding 24 months.
Sauces and prepared foods: Pasta sauces, soups, stews, curry sauces, and ready-to-eat meals packaged in three-piece tinplate cans for retail and food service.
Edible oils: High-volume packaging of cooking oils, where the structural strength of the steel can body is important for large-format containers.
Pet food: One of the highest-volume uses of steel food cans globally, typically using easy-open end (EOE) lids on tinplate can bodies.

Can Body Steel and Sustainability: The Recyclability Advantage

Steel is the world's most recycled packaging material — a fact that makes can body steel not only a functional choice but an increasingly important one from a sustainability perspective. Steel cans can be recycled indefinitely without degradation of material quality, since recycling steel does not alter its fundamental properties.

Because steel is magnetic, it is easily separated from mixed waste streams using standard magnetic sorting equipment, enabling efficient collection without requiring consumer sorting precision. This physical property gives steel packaging a recycling infrastructure advantage over many alternative materials.

For food and beverage brands operating under sustainability commitments — and for governments pushing extended producer responsibility (EPR) legislation — the established recyclability of steel food cans is a significant factor in packaging material selection decisions.