Tinplate sheet and Tin-Free Steel (TFS) are two common metal materials in the modern packaging industry, and are widely used in the canning and packaging of food, beverages, cosmetics and other products. Although both materials are based on steel, there are significant differences in production processes, physical properties, uses, advantages and disadvantages.
In order to help readers better understand the differences between tin plate sheet and Wuxi steel, this article will provide a detailed analysis in terms of material composition, production process, characteristics, application scope, and their respective advantages and disadvantages.
What is a tinplate sheet?
Tinplate sheet, also known as tin plate, is a composite material with a thin layer of tin plated on the surface of steel. Through the electroplating or hot plating process, the low carbon steel is covered with a uniform layer of metallic tin to form a tinplate sheet. The tin layer not only protects the steel from corrosion, but also gives the material good formability and weldability. Therefore, tinplate sheet is widely used in the production of various types of packaging cans.
Tinplate sheet production process
The production process of tin plate sheet mainly includes three steps: steel preparation, tin plating and post-processing.
● Steel preparation: The base material for producing tinplate sheet is low-carbon cold-rolled steel plate. Cold-rolled steel is processed through multiple processes to ensure it has the right strength and toughness.
● Tin plating process: The tin plating process of tin plate sheet can be carried out by electroplating or hot plating. Electroplating tin is the most common method. In an electrolytic bath, steel is used as the cathode and metallic tin is used as the anode. Under the action of electric current, tin is evenly plated on the surface of the steel. Hot tin plating achieves surface tin plating by immersing steel in molten tin liquid.
● Post-processing: The tin plate sheet needs to be passivated after tin plating to enhance its corrosion resistance, and can be coated with a layer of oil or other coatings to increase surface protection and lubricity to facilitate subsequent processing.
Features of tinplate sheet
With its metallic tin layer, tin plate sheet has the following distinctive features:
● Anti-corrosion: The tin layer can effectively isolate the corrosion of steel by air, moisture and acidic substances, giving it good corrosion resistance.
● Weldability: tin plate sheet is suitable for welding and processing, and is suitable for manufacturing various types of sealed cans and other packaging containers.
● Smooth surface: The tin layer not only provides protection, but also makes the surface of the tin plate sheet smooth, suitable for printing various exquisite patterns.
What is Wuxi Steel (TFS)?
Wuxi steel, the full English name is Tin-Free Steel, as the name suggests, is a steel that does not contain tin. Wuxi steel uses a chromium plating process. The surface of the steel is plated with an extremely thin layer of chromium or chromium oxide instead of the metallic tin layer of the tin plate sheet. Wuxi steel is mainly produced through electroplating chromium technology and has good corrosion resistance, wear resistance and a certain hardness.
Wuxi steel production process
The production process of Wuxi steel is similar to that of tin plate sheet, the difference lies in the coating material.
● Steel preparation: Like tin plate sheet, the base material of Wuxi Steel is also a low-carbon cold-rolled steel plate. In order to ensure the mechanical properties of the material, the base material needs to be precision machined.
● Electrochromium plating process: The chromium plating process of tin-free steel forms a composite coating of chromium and chromium oxide on the surface of the steel through electrolysis reaction. This coating can effectively enhance the corrosion resistance of the steel without affecting the mechanical properties of the steel.
● Passivation and lubrication treatment: Similar to tinplate sheet, chromium-plated tin-free steel also needs to undergo passivation treatment to further enhance its corrosion resistance. Subsequently, the surface will also be lubricated to facilitate subsequent stamping and forming.
Characteristics of Wuxi Steel
The chromium layer of Wuxi steel gives it some properties that are different from tinplate sheet:
● Strong corrosion resistance: Although tin-free steel is not protected by a tin layer, the chromium and chromium oxide layers have stronger corrosion resistance, especially in acidic environments.
● Higher hardness: Compared with tin plate sheet, Wuxi steel has higher surface hardness and is suitable for occasions requiring high hardness and wear resistance.
● Unable to weld: Due to the chromium layer on the surface of tin-free steel, the weldability is poor, so it usually cannot be used in the manufacture of packaging containers that require sealing welding.
What is the difference between tinplate sheet and tin-free steel (TFS)?
Although both tinplate sheet and tin-free steel are based on steel and both have anti-corrosion properties, there are significant differences in coating, performance, use and price.
Differences in coating materials
● Tinplate sheet: The coating of tin plate sheet is metallic tin. Tin has excellent corrosion resistance and food safety, so tinplate sheet is particularly suitable for packaging materials that are in direct contact with food, such as food and beverage cans.
● Wuxi steel: The coating of Wuxi steel is chromium or chromium oxide. Chromium plating has better wear resistance and corrosion resistance, but chromium may have safety issues in certain food contact situations. Therefore, Wuxi steel is more used in industrial fields or packaging that indirectly contacts food.
Anti-corrosion properties
● Tinplate sheet: The tin layer can effectively isolate air and moisture from corroding steel, but its acid resistance is relatively poor. Especially in acidic foods (such as fruits and juices), the tin layer is prone to chemical reactions. Therefore, tinplate sheets usually have a coating or protective layer added to the inner wall to enhance their corrosion resistance.
● Tin-free steel: The corrosion resistance of the chromium layer is better than that of the tin layer, especially in acidic environments. Therefore, Wuxi steel is suitable for packaging situations with a lot of acidic substances, such as chemical products, paint containers, etc.
Solderability
● Tin plate sheet: Due to the weldability of the tin layer, tin plate sheet is very suitable for manufacturing packaging containers that require welding, such as sealed cans, beverage cans, etc.
● Wuxi steel: The chromium layer on the surface of Wuxi steel hinders welding, so Wuxi steel generally uses mechanical folding or gluing processes instead of welding when making cans.
Printing effect
● tinplate sheet: The surface of tinplate sheet is smooth and has good printing adaptability, enabling exquisite color printing. Therefore, many brands choose tin plate sheets as food and consumer product packaging to enhance the visual effect of the products.
● Wuxi steel: Wuxi steel has a higher surface hardness. Although it can also be printed, its printing effect and quality are slightly inferior to tinplate sheet. It is generally used for industrial packaging that does not have high requirements for appearance.
Application areas
● Tinplate sheet: Due to the food safety of the tin layer, tin plate sheet is mainly used in food, beverage packaging, cosmetics, medicine and other fields, such as cans, beverage cans, candy boxes, etc.
● Wuxi steel: Due to its corrosion resistance and high hardness, Wuxi steel is more used in industrial fields, such as paint buckets, chemical containers, battery casings, etc. In addition, Wuxi steel can also be used in some food packaging, but it usually requires a layer of barrier coating inside the packaging to ensure food safety.
Price
● Tin plate sheet: Since the price of tin is higher than that of chromium, and the tin plating process is complicated, the production cost of tin plate sheet is relatively high, and the product price is also more expensive than tin-free steel.
● Wuxi steel: Due to the low cost of chromium and the relatively simple process, Wuxi steel has lower production costs and the product price is usually lower than tinplate sheet.