Stainless steel rust problem
Source：YongLiYuan Time：2015-1-17 9:41:25
For some customers currently on the market for stainless steel will rust, with magnetic and some other questions, as well as a magnet for attracting people often think of stainless steel, and to verify the authenticity of their advantages and disadvantages, do not smoke, non-magnetic, considered a good, genuine; suck there are magnetic, is considered to be counterfeit fake, it's a very one-sided, no practical method to identify the error, and that is to suck magnetic stainless iron, stainless steel is not magnetic suction; thus a "stainless steel" and "stainless iron "argument, because there is no on" the existence of this kind of statement of stainless iron ", is now on the market for user queries, a summary of the technical information.
First, why are rusting stainless steel?
In layman's terms, that is not easy to rust stainless steel, in fact, part of the stainless steel, both of stainless steel, but also acid resistance (corrosion resistance). And corrosion resistance of stainless steel is due to its chromium-rich oxide film on the surface (passivation film) formation. This stainless steel and corrosion resistance is relative. Tests showed that the steel in the atmosphere, water or the like medium and weak nitric acid and other oxidizing medium, the corrosion resistance of the steel with the increase of water content of chromium improves, when the chromium content reaches a certain percentage, the occurrence of corrosion resistance of the steel mutations that rust from easy to rust, never corrosion to corrosion. When the surface of the stainless steel tube brown rust (points), people great surprise: that "Stainless steel is not rust, rust is not stainless steel, the steel may be a problem." In fact, this is a lack of understanding of the stainless steel one-sided view of the error. Stainless steel under certain conditions will be rusty. Stainless steel has the ability to resist the atmospheric oxidation of stainless steel --- namely, while also having the acid, alkali, salt corrosion medium is the ability --- namely corrosion resistance. But its size is corrosion resistance of steel itself with its chemical composition, plus mutual status, conditions of use and environmental media type change. Such as 304 steel, in a clean dry atmosphere, there is absolutely excellent anti-corrosion ability, but to move it to the waterfront area, contains a lot of salt in the sea mist, and will soon be rusty; and 316 steel is manifested good. Therefore, not any kind of stainless steel, in any environment corrosion resistant, not rust.
Second, the stainless steel rust reasons
Stainless steel is extremely thin and sturdy fine stable chromium-rich oxide film (protective film) formed by the surface, to prevent the continued infiltration of oxygen atoms to oxidation, and gain the ability of anti-corrosion. Once there is some reason, this film was constantly destroyed, air or liquid oxygen atom will continue to infiltrate or metal from iron atoms continuously analyze, forming loose iron oxide, metal surface rust will continue to suffer. This takes many forms damaged surface film, everyday common are the following categories:
1. Stainless steel surface accumulating the attachments contain other metal elements or heterogeneous metal dust particles, in the humid air, condensate and stainless steel fixtures between the two together into a micro-cell, causing the electrochemical reaction protective film is damaged, call it that electrochemical corrosion.
2. Stainless steel surface adhesion of organic juice (such as vegetables, soup, sputum, etc.), in the case of water oxygen to form organic acids, organic acids prolonged the corrosion on the metal surface.
3. Stainless steel surface adhesion containing acid, alkali, salts (such as wall decoration alkaline, lime splash), causing localized corrosion.
4. air pollution (such as with a lot of sulfides, carbon monoxide, nitrogen oxide atmosphere), the case of condensed water to form sulfuric acid, nitric acid, acetic acid solution point, causing chemical corrosion.
In short, the above situation can be caused by damage to the stainless steel surface protection film caused corrosion. Therefore, in order to ensure a permanent bright metal surface, is not corroded.
First, why are rusting stainless steel?
In layman's terms, that is not easy to rust stainless steel, in fact, part of the stainless steel, both of stainless steel, but also acid resistance (corrosion resistance). And corrosion resistance of stainless steel is due to its chromium-rich oxide film on the surface (passivation film) formation. This stainless steel and corrosion resistance is relative. Tests showed that the steel in the atmosphere, water or the like medium and weak nitric acid and other oxidizing medium, the corrosion resistance of the steel with the increase of water content of chromium improves, when the chromium content reaches a certain percentage, the occurrence of corrosion resistance of the steel mutations that rust from easy to rust, never corrosion to corrosion. When the surface of the stainless steel tube brown rust (points), people great surprise: that "Stainless steel is not rust, rust is not stainless steel, the steel may be a problem." In fact, this is a lack of understanding of the stainless steel one-sided view of the error. Stainless steel under certain conditions will be rusty. Stainless steel has the ability to resist the atmospheric oxidation of stainless steel --- namely, while also having the acid, alkali, salt corrosion medium is the ability --- namely corrosion resistance. But its size is corrosion resistance of steel itself with its chemical composition, plus mutual status, conditions of use and environmental media type change. Such as 304 steel, in a clean dry atmosphere, there is absolutely excellent anti-corrosion ability, but to move it to the waterfront area, contains a lot of salt in the sea mist, and will soon be rusty; and 316 steel is manifested good. Therefore, not any kind of stainless steel, in any environment corrosion resistant, not rust.
Second, the stainless steel rust reasons
Stainless steel is extremely thin and sturdy fine stable chromium-rich oxide film (protective film) formed by the surface, to prevent the continued infiltration of oxygen atoms to oxidation, and gain the ability of anti-corrosion. Once there is some reason, this film was constantly destroyed, air or liquid oxygen atom will continue to infiltrate or metal from iron atoms continuously analyze, forming loose iron oxide, metal surface rust will continue to suffer. This takes many forms damaged surface film, everyday common are the following categories:
1. Stainless steel surface accumulating the attachments contain other metal elements or heterogeneous metal dust particles, in the humid air, condensate and stainless steel fixtures between the two together into a micro-cell, causing the electrochemical reaction protective film is damaged, call it that electrochemical corrosion.
2. Stainless steel surface adhesion of organic juice (such as vegetables, soup, sputum, etc.), in the case of water oxygen to form organic acids, organic acids prolonged the corrosion on the metal surface.
3. Stainless steel surface adhesion containing acid, alkali, salts (such as wall decoration alkaline, lime splash), causing localized corrosion.
4. air pollution (such as with a lot of sulfides, carbon monoxide, nitrogen oxide atmosphere), the case of condensed water to form sulfuric acid, nitric acid, acetic acid solution point, causing chemical corrosion.
In short, the above situation can be caused by damage to the stainless steel surface protection film caused corrosion. Therefore, in order to ensure a permanent bright metal surface, is not corroded.