The Study Of Corrosion Behavior Of Typical Metals By Electric Speckle Pattern Interferometry

The technique based on Electric Speckle Pattern Interferometry （ESPI）,Chronoamperometry, Electrochemical Impedance Spectra （EIS） and linear sweepvoltammetry was applied to study the corrosion behavior of carbon steel inNaHCO3-NaCl-CaCl2solution. An ESPI based technique for in situ and accurateobservation of pitting susceptibility of304stainless steel in NaCl solutions is reportedin this paper. The main results are as following:The influence of carbon steel Corrosion behavior under the Ca²⁺ion of differentconcentrations was investigate by analyzing the average corrosion rate ofchronoamperometry, statistically analyzing the appearance of etch pits and analyzingthe Charge transfer resistanc of EIS. The results indicated that, the Ca²⁺ion on0⁶40mg/L makes a inhibition effect of carbon steel corrosion, When Ca²⁺ionconcentration was640mg/L, Chronoamperometry measured average corrosion rate for3.253E-4A/cm², electrochemical impedance measured the charge transfer resistancefor29.480kΩ·cm², The degree of pit corrosion intensity is2.791, the corrosionbehavior of carbon steel is the slightest.Through analysis the Pitting corrosion inductions time to help identifyspecimens’ pitting resistant. When the solution without Ca²⁺ions, the induction time is88s and the pitting corrosion resistant was the worst. When Ca²⁺ions concentration is0⁶40mg/L,the pitting induction time increases with the Ca²⁺ions concentration andthe pitting risistant increase gradually. When Ca²⁺ions concentration is2560mg/L,the pitting induction time is93s less than640mg/L which pitting induction time is104s. Explain that carbon steel pitting resistance is reduced, but stillis greater thansolution with no Ca²⁺ions.The pitting corrosion sensitivity of304stainless steel in NaCl solution underdifferent Cl-concentration、temperature and pH was studied by Eb′which wasmeasured by ESPI combining dynamic potential linear scanning and EIS. Researchshows that, Time constant τ as smaller as immersion time, Passivation membraneporosity greaten or passivation membrane thickness thin. the pitting corrosionsensitivity of304stainless steel is bigger with the higher Cl-concentration andtemperature, smaller with the higher pH. And when the Cl-concentration is0.01%¹%,Eb′quickly move negative with the increase of concentration Cl-, Eb′moving negative slowing when the Cl-concentration is higher, so the influence had smaller with theincrease Cl-concentrations. when pH is2<pH<7, Pitting potential is moving range ofgentle, pitting sensitivity have a little change, when pH is1<pH<2、9<pH<14, pittingpotential is moving big movments, that is show that the influence of pitting sensitivityare mainly concentrated in this region.