Effect of NaCl-Mg-Cl_2 complex on the corrosion behavior of carbon steel in wet/dry environment

摘要

The iron rust phase has been analyzed by using thein-situ XRD and the alternating current (AC) impedance methodsafter wet/dry corrosion test using NaCl-MgCl_2 complex which ismain composition of airborne saline particles. The corrosion massgain of the carbon steel depends on the concentration of Cl ionfrom environment in the test chamber, and it does not depend onthe type of cations (NaCl or MgCl_2). As the concentration of Clion increases, the content of #beta#-FeOOH increases in iron rustphases. The transition of #beta#-FeOOH from the green rust I(G.R.I) was observed directly by the in-situ XRD. The amount ofG.R.I depends on the concentration of Cl ion, and #beta#-FeOOHis transformed from G.R.I automatically in drying process, wherethere is no dependence of type of cations on the iron rust phasewhichever cation Cl bonds with. It was found by the ACimpedance that the resistance of the rust (R_(rust)) increases withthe number of cycles in the corrosion test, and that the structuralfactor of the rust becomes predominant in R_(rust). With theincrease of the amount of rust, the resistance corresponding tocorrosion rate (R_t) decreases, which is related to the reduction of#beta#-FeOOH in rust phase.