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What materials are stainless steel thermos cups made of?

Stainless steel thermos cups are the most mainstream type of thermal insulation containers on the market. The biggest advantage of stainless steel thermos cups is their excellent thermal insulation performance. High-quality stainless steel vacuum flasks usually use double-layer vacuum technology to form a vacuum layer between the inner liner and the outer shell, which effectively blocks heat conduction and convection, and can keep the temperature of the beverage for up to 6-12 hours. At the same time, stainless steel is extremely sturdy and durable, has good drop resistance, and has a long service life, making it very suitable for outdoor activities and daily commuting.

  • 304 stainless steel

    304 stainless steel is a common material for food-grade stainless steel. It is widely used in many fields such as food, medical care, and home. It contains 18% chromium and 8-10.5% nickel, has good acid and alkali resistance and corrosion resistance, and can resist corrosion from daily beverages such as coffee and tea. However, in high-salt environments (such as pickle soup and seawater), 304 stainless steel has a higher risk of pitting corrosion. Experiments have shown that after 304 stainless steel was filled with lemon juice at pH=3 for 72 hours, the amount of chromium precipitated was still below the national standard limit (0.1 mg/L), which shows that it meets the daily needs of holding different types of drinking water.

  • 316 stainless steel

    316 stainless steel adds 2-3% molybdenum to 304 stainless steel, significantly improving its resistance to chloride ion corrosion. The pitting potential is more than 200mv higher than that of 304, and is particularly suitable for high-corrosion environments such as medical and chemical industries. 316 stainless steel still has no obvious corrosion after 200 cycles of testing in a salt spray environment (5% sodium chloride solution), showing its excellent corrosion resistance. In addition, 316 stainless steel is safer when storing acidic or salty liquids for a long time, and the risk of heavy metal precipitation is lower.

  • 201 stainless steel

    201 stainless steel is already a low-end material that has been eliminated.
    Composition: 16%-18% chromium (Cr) + 3.5%-5.5% nickel (Ni) + 5.5%-7.5% manganese (Mn)
    Features:
     Low cost: low nickel content, cheap price, but poor corrosion resistance.
    Easy to rust: rust spots may appear after long-term use, not suitable for acidic or carbonated beverages.
    Not recommended for long-term use: some inferior thermos cups may use 201 stainless steel to impersonate 304, so be careful to distinguish.

  • 316 stainless steel has higher corrosion resistance and heat resistance

    Corrosion resistance‌. Due to the addition of molybdenum, 316 stainless steel has 10 times higher resistance to chloride ion corrosion than 304, and has a higher pitting potential, so it performs better in high humidity and high salt environments. 304 stainless steel has a higher risk of pitting in high salt environments‌.
    ‌Heat resistance‌. 316 stainless steel can withstand high temperatures of up to 1200-1300℃ without losing its strength and corrosion resistance, while the operating temperature range of 304 stainless steel is relatively narrow, generally between -196℃ and 800℃.

Choose 304 stainless steel or 316 stainless steel?

‌Daily use‌. If it is mainly used to hold hot water or neutral drinks, 304 stainless steel is safe enough and more economical.

‌Special needs‌. If you need to store acidic drinks (such as lemonade, sour plum soup), electrolyte drinks for a long time or live in coastal areas, it is recommended to choose 316 stainless steel to ensure higher corrosion resistance and safety.

How to identify stainless steel materials?

Check the logo. The inner liner of a regular thermos cup will be marked with “304”, “316” and other steel stamps.

Magnetic test. 304/316 stainless steel is non-magnetic or weakly magnetic, and 201 stainless steel is more magnetic.

Chemical testing. Stainless steel testing chemicals can be dropped on the inner tank. The color change can be used to determine the material (304 turns red, 201 turns black).

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