Stainless steel rusting occurs

Stainless steel , by definition refers to the resistance of air , steam, water and other corrosive medium and weak acid, alkali , salt and other chemical etching medium corrosion of steel , also known as acid-resistant stainless steel. But in the practical application of them , and some stainless steel but the accident rusty . Stainless steel rusting occurs , there may be several reasons:
First, between the natural corrosion.
This material does not contain titanium and niobium have a tendency to intergranular corrosion. Adding titanium and niobium, together with the stabilization process can reduce intergranular corrosion. Corrosive chemicals in the air or in a high- alloy steel resistant to corrosion , stainless steel is a beautiful surface and good corrosion resistance , without going through the plated surface treatment, and play inherent in surface properties of stainless steel , for use in multi- an aspect of steel , stainless steel is often called . Representative of the performance of 13 chrome steel , 18-8 chrome -nickel steel alloy . From the perspective of metallographic analysis , because the stainless steel contains chromium chromium film formed on the surface leaving a thin , the membrane separating the oxygen from corrosion-resistant steel intrusive role . To maintain the inherent corrosion resistance of stainless steel , the steel must contain more than 12 % chromium. The need for welding applications. Lower carbon content makes it close to the weld heat affected zone to minimize carbide precipitation , and carbide precipitation may lead to intergranular corrosion of stainless steel welded erosion in some environments .
Second , without solution treatment.
No alloying elements dissolved in the matrix , resulting in tissue matrix alloy content is low, poor corrosion resistance.
Thirdly, the presence of chloride ions in the environment .
Widespread presence of chloride ions , such as salt / sweat / sea / sea / soil , and so on . Stainless steel in the presence of chloride ions in the environment, the corrosion rapidly , even more than the ordinary low carbon steel. Therefore, the use of stainless steel environment requirements, and require frequent cleaning to remove dust, keep it clean and dry.