Why does the stainless steel get rusty too? ----Reason page
    For a long time, consumers find a phenomenon of appearance of stainless steel getting rusty, cause the customer to produce certain doubt to the products. Aiming at this situation, according the consultation to professional personage, we make everyone know the reason of "the stainless steel gets rusty".
    Why does the stainless steel get rusty too? When the brown rusty spot (dot) appears on the surface of stainless steel, people are very surprised: they supposed “the stainless steel does not get rusty and it is not the stainless steel getting rusty, so it may be the steel goes wrong ". In fact, this is a one-sided and wrong view of lacking of understanding to the stainless steel. The stainless steel will get rusty on certain terms, too.
    The steel not getting rusty in such medium of weak corrosion as air, water, steam, etc. is called stainless steel. The stainless steel is smelted by adding chromium element of certain content in the general carbon steel. The key point that the stainless steel has nature of stainless is that there is an element called chromium in the steel. Under the function of corrosive medium, chromium causes the steel make a layer of firm and compact membrane of oxide on the surface, called "the passivation membrane". This membrane isolates the metal from external medium and prevents the metal from being corroded further. Also it has the ability that repairs itself. If destroyed, the chromium in the steel will turn into the passivation membrane with oxygen in the medium again , continuing the protection.
    The stainless steel has the ability of resisting atmosphere oxidization –that is the rustproof nature, at the same time it has the ability of resisting corrosion in the medium of acid, alkali, salt –that is inoxidizability. Generally speaking, the stainless steel will not get rusty, but improper use or improper maintain, or the execrable environment that the stainless steel may appear the phenomenon of getting rusty. Seeing yellow or orange rusty spot on surface of steel, we can quickly make sure that is the sign of getting rusty. The inoxidizability of stainless steel changes according to the change of the nature of chemic element, state of mutually add, using condition and environmental medium type.
Stainless steel obtains the inoxidizability form the extremely thin but firm and oxidize membrane rich in chromium (protective membrane) on its surface, which prevents it from continuative permeating of oxygen atom, continuative oxidizing. Once this kind of membrane has been destroyed constantly for certain reason, the oxygen atom in air or the liquid will be permeated constantly or the iron ion in metal is being isolated out constantly, then form the loose ferric oxide, so the metal surface is being corroded constantly. There are a lot of forms that this kind of surface membrane is destroyed, several kinds of which are familiar in daily life are as follows:
1. In the moist air, the dust of other metallic elements or adhesive material of alien metal granule stockpiled on the surface of stainless steel turn the adhesive material and the condensation water to a tiny battery, which caused electrochemistry reflection, so the protective membrane has been destroyed. That is called electrochemistry cauterization. (If you put the stainless steel and iron together for a long time in daily life, two kinds of situations will be produced 1. The stainless steel becomes rusty soon. 2. The stainless steel becomes the steel with magnetism.)
2. Under the condition of water and oxygen, the liquid of organic substance adhered in the surface of stainless steel (such as melon and dish, soup of noodle, phlegm, etc) forms organic acid. It will cause the organic acid to corrode the metal surface after a long time.
3. The sour, alkali, and saline material adhered on the surface of stainless steel (such as buck on the wall of fitment, splash of lime wash) cause the part cauterization.
4. In air being polluted (such as air containing a large number of sulphides, atmosphere oxidizing carbons and oxidizing the nitrogen), meeting the condensation water, it will form sulphuric acid, nitric acid and acetic acid liquid drop which cause chemic cauterization. (It will speed up the phenomenon while living in the environment with heavy pollution of close to seashore)
5.  The steel brush, the metal line brushes and metal chip, etc. rubbing the surface of stainless steel will cause the abrasion of surface.
6. The decolourant in the water, food and salt, among which the worst one comes from family expenses and industrial sanitizer, will cause the top layer of stainless steel damaged, too.
    The above-mentioned situations may cause the phenomenon of getting rusty of the stainless steel.