Crevice Corrosion Behavior Of Q345E Steel In Simulated Seawater Solution

Crevice corrosion can conceal so well in the early stage that cause sudden failure anda huge economic loss constantly. Crevice corrosion occurs mainly due to the effect ofchlorine ion, under the electric field force the chlorine ion migrate into the deep creviceand destroy the metal passivation state formed the occluded cell, then its autocatalyticeffect result in serious corrosion of metal. Applying rectangular crevice model to studythe crevice corrosion behavior of Q345E steel and the role of impressed current cathodicprotection in simulate seawater solution. The law of crevice corrosion and corrosionmechanism were revealed.First of all, to defined the corrosion behavior of Q345E steel in simulated seawatersolution(3.5%NaCl) at different time studied the self corrosion potential, corrosion rate,EIS and polarization curve, also observed the corrosion morphology of macrography.According to the research, corrosion degree of Q345E steel was aggravating with time.Corrosion rate is higher in the early time and decreased with the accumulation of corrosionproducts. Electrochemical testing results accord with the actual corrosion behavior.Secondly, by using rectangular crevice model, electrochemical impedancespectroscopy and scanning electron microscope (SEM) studied the marine corrosionbehavior in the crevice. The results show that with corrosion time extending electrodepotential in the crevice decreased and Cl-concentrations increased gradually. The changingof Cl-concentration at the bottom was the most obviously and the value is the maximum.When narrow the size of the crevice electrode potential is more negative and the Cl-concentration is greater.Finally, to define the cathodic polarization characteristics of Q345E steel in the creviceanalysed the polarization time, cathodic polarization control potential, crevice thicknessesand concentration of NaCl solution various factors on the polarization potential,polarization current density. Results demonstrated that polarization potential andpolarization current density at different distances were decreased with time goes on. When the opening control potential decreased or the size of crevice increased, polarizationpotentials is shifted negatively and polarization current density increased gradually. Withthe Cl-concentration of the bulk solution decreasing, polarization potential in the creviceof the sample increased, the polarization current density decreased.