The Study On The Corrosion Characteristics Of Aluminum And Chromium Alloying J55Steel

Regarded as backing material, J55carbon steel is smelt into two types of low alloy steelwith high aluminium and chromium through vacuum melting in this paper. Corrosionresistance is studied by using electrochemical methods such as potentiodynamic polarizationcurve, electrochemical impedance spectroscopy, etc as well as immersion test. The results ofexperiments show:The open circuit potential value Eocp of developed steels of static state, compared withthat of J55carbon steel, turn to a more positive and thermodynamic stability. Under thedynamic corrosion condition,the developed Steels show higher thermodynamic stability thanthat of J55carbon steel. developed steels and J55carbon steel share the same electrochemicalcorrosion mechanism and both belong to activation anodic current dissolution. But, with theincrease of electrochemical polarization resistance, free corrosion current density of developedsteels decrease and show high electrochemical corrosion resistance. After the pre-corrosion,the corrosion mechanism of steels change and the formation of corrosion products block thereaction of cathode and anode. Thus, developed steels show better corrosion resistance thanJ55carbon steel. In simulated solution and3.5wt.%NaCl solution, the electrochemicalimpedance spectroscopy of developed steels are capacitive reactance arc with two timeconstants, J55carbon steel corrosion is under the hybrid control of activation polarization andconcentration polarization. After the pre-corrosion, the polarization resistance Rp of developedsteels are bigger than that of J55carbon steel. In the3.5wt.%NaCl solution, with the increaseof solution temperature, polarization resistance of three types of steel all decreases firstly, andthen increases and has a minimal value at about60℃. With the same solution temperature, thepolarization resistance of developed steels are always bigger than that of J55carbon steel andshows better corrosion resistance. In the static simulated solution, steels are dominated byuniform corrosion and corrosion rate of developed steels are far below that of J55carbon steel;in the static3.5wt.%NaCl solution, developed steels show local corrosion with a lowercorrosion rate than J55carbon steel and low-Cr steel. The results of the energy spectrumanalysis shows that on the surface of developed steels, the protective corrosion product gathering aluminium and chromium is formed that increases the material’s ability to resistcorrosion. In the dynamic corrosion condition, corrosion rate of steels is greatly increased, butdeveloped steels have a relatively low uniform corrosion rate and localized corrosion depththan J55carbon steel and low-Cr steel.