Only when the weight ratio of chromium in the material reaches 12.5% can it be called stainless steel, and only when the chromium content reaches 18% and the nickel content reaches 8% can it have the corrosion resistance and rust resistance required by edible stainless steel utensils. According to this standard, the content of manganese is naturally lower than 2%. Under this content ratio, stainless steel is not easy to rust, and the precipitation of chromium, nickel and manganese will not endanger human health. However, if manganese is used instead of nickel, the oxidation protective film of chromium on the surface of stainless steel is easy to be destroyed, and metals such as chromium, manganese and nickel are easy to precipitate excessively. Therefore, the key to the heated safety debate in stainless steel pot at present lies in the low chromium and nickel content and high manganese content of the product itself. Chromium, nickel and manganese are not difficult to precipitate, but the higher the stability, the less easy it is to precipitate. Unqualified stainless steel products not only have the potential danger of manganese escaping, but also the danger of excessive release of nickel and chromium. Therefore, reaching the standard dose is the basic prerequisite for safe use.
Raw material cost accounts for 70-80% of stainless steel cost. Therefore, the rise in the price of nickel-chromium raw materials directly affects the production cost. Merchants use some brands of so-called stainless steel in order to reduce costs. Its nickel content is even only? 1% or so, because consumers mistakenly think that stainless steel without magnetism is stainless steel, in order to achieve this non-magnetic characteristic and reduce chromium content, such stainless steel has worse corrosion resistance and is more prone to rust. During this period, the added chromium and nickel, as well as manganese and other metals, can easily migrate out of eating utensils, pollute our food and endanger our health in quiet places. Especially at the high temperature of cooking, combined with the acidic characteristics of ingredients and alkaline conditions of washing, the migration is smooth.
Manufacturers can claim that their pots have not exceeded the standard in the experiment of heavy metal migration, but it is not difficult to imagine that the pots submitted by manufacturers must be new. Our laboratory soaked in 4% acetic acid solution, and detected the migration of various metals in stainless steel kitchenware by inductively coupled plasma mass spectrometry. It is found that the migration of the old pot is dozens of times that of the new pot. Experiments show that even if the content of stainless steel is greatly reduced and not up to standard, most of the migration detected at the time of purchase is up to standard, but with the passage of time, the migration has doubled, as is the case with brand products. Of course, it is self-evident that those stainless steel vessels that cry for loss 10 yuan are above. The ability of naive stainless steel products to resist the erosion of time is quite tenacious and trustworthy. It is understandable for manufacturers to pursue profits and reduce costs, but the products made by consumers cannot release toxic and harmful substances, which is an insurmountable bottom line.
Because of the film "erin brockovich" starring Julia Roberts, the harm of chromium has been deeply rooted in people's hearts, and the harm of preserved milk, which once made a lot of noise, also lies in chromium, so I won't go into details here.
At present, no cases of dietary nickel deficiency caused by normal diet have been found, so there is no need to supplement nickel. We need to be alert to excessive nickel intake. The allergic reaction and carcinogenic toxicity of nickel to human body have attracted great attention from European and American medical and material circles. It has become a climate to prohibit the use of nickel alloy to manufacture products that come into contact with human body. However, we mentioned earlier that in order to stabilize stainless steel, nickel must be added to a certain amount. Therefore, after the nickel-free revolution of medical implant materials and the widespread popularization of nickel-free electroplating, nickel-free stainless steel tableware will also be the inevitable orientation. But it should be emphasized that it is a poor choice to remove nickel and simply replace it with manganese.
Although manganese is an important trace element necessary for human body, excessive manganese can also cause poisoning. Of course. Like other essential trace elements, taking people from food alone will not cause manganese poisoning. Chronic manganese poisoning is a progressive and irreversible disease, which is changing from clinical type to subclinical type at present, and it is very hidden. The absorption rate of manganese in digestive tract is very low. In addition to escaping from stainless steel utensils, it is more important to be alert to respiratory intake, which is the main intake channel. For example, manganese methylcyclopentadiene tricarbonyl, which has been used to replace tetraethyl lead as gasoline antiknock agent, is spreading to the environment at an unprecedented speed with the increasing automobile exhaust every day. Therefore, the release of manganese in the new national standard of stainless steel tableware needs to be improved. Now some countries should not only test the manganese content, but also test the iron content.
Summary statement: Pure stainless steel is just an advertising language. Generally speaking, stainless steel refers to steel that can resist the corrosion of weak corrosive media. The annual corrosion rate less than 0.0 1mm is called complete corrosion resistance, and the corrosion rate less than 0. 1mm is called corrosion resistance. So stainless steel can't corrode, but it corrodes slowly. There is no need for mythical stainless steel, superstitious stainless steel, and other safe traditional kitchen utensils, which also exudes fashionable charm.
When we buy stainless steel tableware, we can look at the logo on it. Of course, some stainless steel products are not available. There are three codes: 13-0, 18-0 and 18-8. The number before the code represents chromium content, and the number after it represents nickel content, as mentioned above, 65438.
Do not use stainless steel tableware to cook acidic food at high temperature for a long time, let alone decoct traditional Chinese medicine, and do not use strong alkali or strong oxidizing chemicals to clean it. The antirust principle of ordinary iron products is applicable to stainless steel. Stainless steel can be completely recycled, so the speed of family renewal must exceed the corrosion speed in stainless steel pot, especially the fake stainless steel pot whose nickel and cadmium contents are not up to standard, which should be paid more attention to. If the manufacturers who produce unqualified products can get lost, then the best crisis public relations is to trade in the old for the new. Extensive and vigorous development, only recognize the pot, regardless of the invoice. ?
Cleaning of compound stainless steel pot;
All metal surfaces exposed to corrosive environment have electrochemical reactions or chemical reactions, which are uniformly corroded. When cleaning the stainless steel surface, pay attention to avoid scratching the surface, and avoid using bleaching ingredients and abrasive cleaning solutions, steel balls, abrasives, etc. To remove the cleaning solution, please rinse the surface with clean water at the end of cleaning. ?
If there is dust on the surface of stainless steel, the dirt can be easily removed and can be cleaned with soap, weak detergent or warm water. The trademarks and films on the surface of stainless steel should be cleaned with warm water and weak detergent, and the adhesive components should be scrubbed with alcohol or organic solvents (ether, benzene). ? Grease, oil and lubricating oil pollution on the surface of stainless steel should be cleaned with a soft cloth, and then with neutral detergent or ammonia solution or special detergent.
Bleach and various acids adhere to the surface of stainless steel. Wash it with clear water immediately, then dip it in ammonia water solution or neutral carbonated soda water solution, and wash it with neutral detergent or warm water. ?
There are rainbow lines on the surface of stainless steel, which is caused by excessive use of detergent or oil. When washing, you can wash it off with warm water neutral detergent. ? Rust caused by dirt on the surface of stainless steel can be cleaned with 10% nitric acid or grinding cleaner, or with special cleaning drugs.
Tip:
Mirror stainless steel is best not to be cleaned with liquid medicine as a last resort, nor to use a good universal cleaner.
As long as chemicals are used, they will generally have a certain impact on stainless steel products. Stainless steel, like Lishi, has different materials and chemical composition even if it is the same batch of products. For example, mirror stainless steel, if cleaned with chemicals, the surface of stainless steel will sometimes turn black because of the oxidation of the material.