Spider fittings raw material is stainless steel 304 or 316,this is two kinds material difference following:
  Form of iron oxide in carbon steel to oxidation, so rust growing and eventually the formation of holes. We can use paint or oxidation-resistant metal (for example, zinc, nickel and chromium) were plated to ensure the steel surface, but, as people know it, this protection is only one kind of film. If the protective layer is damaged, the following steel began to rust, so was born the stainless steel.
    Depends on the corrosion resistance of chromium stainless steel, but because chromium is a component of the steel, so the protection methods vary.
    Add in the chrome reached 10.5%, the atmospheric corrosion resistant steel increased significantly, but the chromium content higher, although still improve corrosion resistance, it is not obvious. The reason is the steel with chromium alloying processing, the surface oxide into the type of change is similar to pure chromium metal oxides formed on the surface. This tight adhesion of chromium-rich oxide to protect the surface against further oxidation. This very thin oxide layers, it can be seen through the natural shine of steel surfaces, so that stainless steel has a unique surface. Moreover, if damaged surface, the exposed steel surface and atmospheric response to self-repair, re-formation of this passive film, continues to play a protective role.
    Therefore, all of stainless steel have a common characteristic, that is, chromium were above 10.5%.
And building construction applications of steel are usually only about six. They contain 17 to 22% chromium, better steel also contains nickel, such as 304. Add the atmospheric corrosion of molybdenum can be further improved, in particular resistance to atmospheric corrosion with chloride, 316 fall into this category. Ni-Mo alloy has excellent corrosion resistance.
      In polluted industrial areas and coastal areas, the surface is very dirty, even from corrosion. But to get the aesthetic effect of outdoor environments, would need to use nickel-containing stainless steel. Therefore, 304 stainless steel is widely used in curtain wall, side walls, roof and other construction purposes, but in the erosion of serious industrial or marine atmosphere, preferably 316 stainless steel.