Effect of Al/Si on corrosion resistance of corten steel tube under marine atmospheric environment

Researchers still have a lot of controversy about whether Si can improve the weatherability of steel. The studies have found that large particles α-Fe2O3 and magnetic α-FeOOH can hinder the formation of protective rust layer and increase the corrosion rate of carbon steel. On the contrary, the corrosion rate of carbon steel decreases due to the refinement of particles by superparamagnetic α-FeOOH.

In addition, the corrosion resistance test of carbon steel under simulated industrial atmospheric environment shows that the addition of Si will deteriorate its corrosion resistance. In recent years, corten steel tube with high content of Si and Al has been studied in Japan, a coastal island country. A kind of ultra-fine grain corten steel tube with high content of Al and Si has been developed. The steel has better corrosion resistance in the environment containing chloride ions. Researchers believe that the excellent corrosion resistance of the corten steel tube mainly depends on the chemical composition, that is, high content of Al and Si, followed by ultra-fine grain structure. By analyzing the composition of the rust layer, it is found that the complex oxides of Al and Si exist in the inner rust layer in the form of divalent and trivalent respectively. The nano-scale complex oxides containing Al and Si are more abundant in the inner rust layer by scanning electron microscopy. It is precisely because the formation of nano-scale complex oxides containing Al and Si in the inner rust layer can increase the charge and mass transfer resistance, thus inhibiting the corrosion process of corten steel tube.