Every day we deal with more than 10 years of stainless steel stainless steel. Usually,people are just as its name implies that it is a rustless metal.In fact,the truth is actually zayang?? and listen to Jingxin hardware professional engineers for you to decrypt:

Stainless steel is not not to rust, but the relative to other aluminum, iron, copper, metal, corrosion resistance is better.

The current market all stainless steel does not rust mechanism is due to the presence of Cr element.The fundamental cause of the corrosion resistance of stainless steel (mechanism) is a theory of the passivation film.The so-called passivation film is on the surface of the stainless steel with a layer of Cr2O3 film.Due to the film in the presence of stainless steel base body blocked corrosion in a variety of media,this kind of phenomenon called for the passivation.

The passivation film formation of two cases,a is stainless steel itself is self passivation ability,the self passivation ability increases with the increase of the chromium content and speed up.Therefore,it has the anti rust;another over a wide range of formation conditions is stainless steel in various aqueous solution (electrolyte),in corrosion process in the formation of passive film and the corrosion blocked. When the passive film is damaged immediately and form a new passivation film.

Stainless steel passivation film has the ability to resist corrosion.

Under certain conditions,the stainless steel will be corroded.

So the application environment is extremely complex and simple oxidation chromium passivation film still can not meet the high corrosion resistance requirements.Thus,according to the use condition of different need in steel by adding molybdenum (MO),copper(Cu),nitrogen(n)and other elements,in order to improve the composition of the passive film,to further improve the corrosion resistance of stainless steel.

Addition of Mo,due to corrosion products MoO2 near the substrate and passivation of strongly promoting collective,to prevent the corrosion of the matrix;make stainless steel surface passivation film containing CuCl Cu addition,because it and corrosive medium will not take effect and improve the corrosion resistance;add n,due to the passivation membrane enriched the Cr2N,passivation film of Cr concentration increased,so as to improve the corrosion resistance of stainless steel.
 

In fact, the corrosion reaction of stainless steel is a kind of sensitization phenomenon.

Stainless steel containing Cr in the surface form of chromium oxide thin films,lost active chemical,known as passivation state,but austenitic if after 475~850 DEG C temperature range C will combined with Cr precipitation of chromium carbide (Cr23C6) is generated in the crystal boundary, so near the grain boundary Cr content greatly reduced,a CR depleted zone.At this time,the resistance corrosion will reduce,the corrosive environment are particularly sensitive, so that for sensitization.Sensitization in acid oxidation environment are most prone to corrosion,in addition to welding heat affected zone and thermal bending processing zone.

So,what is the case of stainless steel corrosion?

According to our experience,the general conditions of the corrosion of stainless steel include: 

1.different grades of stainless steel material properties:the physical and chemical properties of materials,such as 201 304 and 316 stainless steel is relatively easy to rust.

2.Applicable environmental conditions:temperature,humidity,fluid speed,oxygen content and pH value,the greater the air humidity,the greater the temperature difference,the more easily the stainless steel rust.

3.The corrosion media:acid,alkali,salt,oxide,organic and microbial contact,strong acid and alkali chemical contact, long-term place away from the sea,high humidity and high salinity,stainless steel is more prone to rust.

Therefore,we do not have to worry too much, the corrosion resistance of stainless steel is conditional.

Only a grade stainless steel in a medium is corrosion, but in another medium may destroyed. So the corrosion resistance of stainless steel is a relative concept,so far,there is no a stainless steel in all environments are absolutely not corrosion. 

Please note:the use of stainless steel products,in addition to the pre buy as far as possible to choose the more excellent the most suitable varieties of stainless steel,the latter must pay attention to cleaning products,maintenance and maintenance,which to prevent stainless steel rust is crucial.

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