Including Na₂S₂O₃’s Alkaline Solution Impacts On The Corrosion Behavior Of 16Mn And Q235 Steel

The equipment of alumina production technology need to resist high temperature, high alkali, high pressure.As the equipment,16 Mn and Q235 steel have a good comprehensive performance and the cost is appropriate.In recent years,due to the high grade bauxite resources are increasingly scarce,the mining intensity of high sulfur bauxite is gradually heavy.The sulfur’s continuous transformation and accumulation in the process of production of equipment caused serious corrosion effect and reduced the service life of equipment. Studying the corrosion behavior of 16 Mn and Q235 steel has the extremely vital significance so that we can take corresponding measures to reduce the risk.Corrosion test on 16 Mn and Q235 steel by salt-spray corrosion was studied. Analysis on the influence of corrosion time and sulfur’s concentration to the corrosion weight loss and corrosion depth and electrochemical corrosion behavior of corrosion samples.The main conclusions are as follows:(1) Corrosion morphology of 16 Mn and Q235 steel was pitting corrosion. With the extension of corrosion time from 1d to 9d and the rise of sulfur’s concentration from 3g/L to 7g/L,the value of corrosion weightlessness rate and pitting depth first increases and then decreases,finally reachs to a stable state. The value of 16 Mn corrosion weightlessness increased from 5.1616g/m2 to 5.8874 g/m2, the value of Q235 corrosion weightlessness increased from 5.1616g/m2 to 5.8874 g/m2 in the NaOH solution, The value of 16 Mn corrosion weightlessness increased from 2.4283g/m2 to 2.6420 g/m2, the value of Q235 corrosion weightlessness increased from 1.2478 g/m2 to 1.4337 g/m2 in the NaAlO2 solution. 16 Mn steel’s corrosion is more serious than Q235 steel.In the NaAlO2 solution steel’s corrosion is more serious than in the NaOH solution.(2) In the NaOH solution,corrosion products consist of O, S, Fe elements.In the process of corrosion,the percentage of O element is high,about 30%~40%,with the extension of corrosion time and the rise of sulfur’s concentration,the percentage of S element increased slightly,accounted for 5%. In the NaAlO2 solution,corrosion products consist of O, S, Al,Fe elements.(3) From analysis of polarization curve and AC impedance spectra: with the extension of corrosion time and the rise of sulfur’s concentration, corrosion current density rised gradually, after corroded 9d,corrosion current density maintains 5uA/cm2, capacitance arc radius declined,charge transfer resistance declined. In the NaAlO2 solution the value of charge transfer resistance is smaller than in the NaOH solution.