Study on Corrosion Resistance of Steel Tube for Evaporator Pipe Bundle

Since the corrosion resistance of carbon steel is insufficient in Bayer alumina process,the low alloy steel for corrosion resistance is developed by adding Cr,Cu and other elements.The comprehensive evaluation and analysis of micro-structure,mechanical property and corrosion resistance are carried out.The results show as follows:for improving corrosion resistance in dilute sulfuric acid,BGNDMA and BGAABC are low alloy steel,which corrosion resistance of hot rolled state is equivalent to that of heat treatment state,unlike spheroidized A179 carbon steel.The micro-structures of BGNDMA and BGAABC are still ferrite & pearlite like carbon steel.The corrosion resistance of BGNDMA and BGAABC in dilute sulfuric acid is at least four times higher than that of carbon steels such as 20G and A179 in 6% & 10.3% H₂SO₄ solution at 60℃.BGNDMA and BGAABC can completely replace 20G and A179 carbon steels in dilute sulfuric acid corrosion environment such as alumina industry.Corrosion rates of evaluated low alloy steels are lower than 1.0 mm/a in 20% NaOH solution at 125℃,while BGAABC is lower than 0.1 mm/a,and no alkali fragile occurs.