Will 304 stainless steel rust after welding?

304 stainless steel composition in addition to iron, there are chromium, nickel, aluminum, silicon and so on. Scientists have found that the more uniform the internal structure of steel, the more closely the various components are linked, the more difficult it is for corrosives to invade, the content of alloying elements, generally speaking, the content of chromium in 10.5% of steel is not easy to rust. The higher the content of chromium and nickel corrosion resistance is better, such as 304 material nickel to be the content of 8-10%, chromium content of 18-20%, such 304 stainless steel welding is not rust.

Coupled with the surface and attached to a layer of oxide protective film, just like the armor to the steel, nature is not easy to rust. Stainless steel is relying on its surface to form a layer of extremely thin and strong and dense stable chromium-rich oxide film (protective film), to prevent oxygen atoms continue to penetrate, continue to oxidize, and obtain the ability to resist corrosion. But for some reason, this film is constantly destroyed, air or liquid and oxygen atoms will continue to penetrate or metal iron atoms continue to separate out, the formation of loose iron oxide, metal surface is also subjected to constant corrosion. The surface film is damaged in many forms, and there are several kinds as follows:

1、 Stainless steel surface accumulation contains other metal elements of dust or dissimilar metal particles of adhesion, in the humid air, adhesion and stainless steel condensation, will be connected to a microcell, triggering an electrochemical reaction, the protective film is damaged, known as electrochemical corrosion.

2、 Stainless steel surface adhering to organic sap (such as squash, noodle soup phlegm, etc.), in the presence of water and oxygen, constituting organic acids, long time is the formation of organic acids on the metal surface corrosion.

3、 Stainless steel surface adhesion containing acid, alkali, salt substances (such as alkaline water, lime spray test) caused by local corrosion.