Stainless steel is an alloy composed of various metal elements, of which "chromium" is the most important soul, because it will form a protective film of chromium oxide on the surface to achieve the effect of rust prevention. It must contain at least 11% of "chromium" in order to be called "stainless" steel, which has the characteristic of not easily rusting. Another major player is "nickel", which is the best material for corrosion resistance.
According to the different proportion of the two protagonists of "chromium" and "nickel", stainless steel can be divided into 200, 300, 400 and other series. 200 series stainless steel contains less expensive mulberry "nickel" element, so the price is lower, but also relatively easy to rust. The 300 series is the most widely used grade with high content of chromium and nickel and its firmness and durability. The 400 series has a wide range of components and is difficult to generalize.
304 and 316 stainless steel are the first choice for tableware.
For bento boxes and other tableware, 304 and 316 stainless steel are the most suitable. 304 stainless steel, commonly known as "white iron" in Taiwan, has good corrosion resistance and is the most versatile, including industrial, furniture decoration industry and food and medical industry.
316 medical grade stainless steel is the second most versatile stainless steel because it contains one more element of molybdenum (Mo) than 304 stainless steel, making it more corrosion resistant, stronger, and more expensive. It is suitable for fertilizer production equipment, photographic, food industry, and coastal facilities.
Tips : How to distinguish stainless steel with magnets?
316 stainless steel has no magnetism at all; 304 stainless steel may have weak magnetism because of processing, but it is not possible for strong magnetism.Therefore, if the magnet can absorb it, it is 430, and if it feels weak magnetism, it is 304.
430 stainless steel meets food grade standards and is less expensive
430 stainless steel does not contain nickel, the price is lower than 304 and 316 stainless steel, commonly used in kitchen utensils, dishwashers and the inner layer of washing machines. However, its corrosion resistance is not as good as 304 and 316 stainless steel, and it is easier to rust with long-term use.430 stainless steel has good corrosion resistance to nitric acid, which is most widely used in the fields of automobile accessories and related components. When distinguishing, you can use a magnet to absorb the bottom of the appliance. If you can absorb it, it is 430 stainless steel. If you can't absorb it, it may be 304 or 316 stainless steel.
The 200 series is more likely to rust, but the FDA says there are no safety concerns.
Some rumors that 200 series are industrial stainless steel, as tableware will release toxic substances, this is a biased concept. 200 series of corrosion resistance is not as good as 304 and 316, but not all are harmful.Food and Drug Administration officials said that the 200, 300 and 400 series of stainless steel containers were used in the dissolution test, 200 series of stainless steel material dissolved no difference with the other two, so 200 series of stainless steel and will not be due to high temperature or intolerance of general food acid alkaline value and the dissolution of harmful substances.However, 201,202 stainless steel is seldom used for tableware and mostly for industrial use because of its high manganese content, extremely low nickel content and poor antirust effect.It is recommended to pay attention to the selection of tableware.
What needs to be made clear is that 200 series cutlery will not dissolve too much "manganese" metal because of serving food.According to the results of the manganese dissolution test conducted by the FDA in 101 for different materials of stainless steel, if 4% acetic acid is used as the solvents (at 60°C for 30 minutes) and the highest manganese dissolution level is 4.39 ppm (mg/kg) for 200 series steel, for example, the intake of manganese from a bowl of 200g soup (in 200 series stainless steel container) is only 0.88 mg, which is much lower than the intake of manganese from a bowl of brown rice (based on 80g brown rice) (3.77 mg). This is much lower than the intake of manganese (3.77 mg) from a bowl of brown rice (80 g of brown rice).Although there are many negative rumors about 200 series stainless steel on the Internet, there is no scientific proof that it is harmful to the human body, and the public need not worry too much.
204Cu stainless steel has the same properties as 304stainless steel.
AISI 204Cu stainless steel has the best performance in the 200series, so it is suitable to be used as tableware such as bento boxes. Its performance is very close to that of 304 stainless steel, but the price is cheaper and the performance-to-price ratio is quite high.Strong 204Cu stainless steel is less prone to scratching and wear than 304 and 430, making it the best alternative to 304 stainless steel and superior to 430 stainless steel. 204Cu stainless steel is less common in Taiwan, but many brands in the U.S. use it to make bento boxes and other tableware.