Why does stainless steel rust?
Author： Date：2016-09-21 From： Hits：1860
Not only simple but in stainless steel rust exposed to chlorine and other harsh environment, or the appearance of the passivation layer by mechanical or chemical damage, than usual to rust, so you see stainless steel rust is not strange. With the days of Baocheng stainless steel Baocheng stainless steel are made of chromium passivation, the thickness of the oxide film on the surface of the surface than fresh natural oxide film thickness, also more dense.
All metals are reacted with oxygen in the atmosphere to form an oxide film on the surface. Unexpectedly, the iron oxide is formed on the general carbon steel to continue oxidation, so that the corrosion continues to expand, and ultimately constitute a hole. It can be used to protect the surface of carbon steel by using paint or oxidation resistant metals (e.g., zinc, nickel and chromium), but, as you know, this is only a thin film. If the protective layer is damaged, the steel began to rust Chrome is made of stainless steel has the basic elements of corrosion resistance, when the Cr content in steel reaches about 12%, the oxygen effect of chromium and corrosive medium, form a thin film on the steel surface (self passivation film), the matrix can prevent further corrosion of steel the. In addition to chromium, the commonly used alloy elements are nickel, molybdenum, titanium, niobium, copper, nitrogen and so on, in order to meet the needs of various uses for stainless steel arrangement and function.
The corrosion resistance of stainless steel decreased with the increase of carbon content, and therefore, most of the carbon content of stainless steel is lower, some of the steel wC and even less than 0.03% (such as 00Cr12). The main alloying element in stainless steel is Cr, only when the Cr content reaches a certain value, the corrosion resistance of the steel. Therefore, the stainless steel is generally more than 13% wCr. Stainless steel is also rich in Ni, Ti, Mn, N, Nb and other