Passivation Behavior of Laser Selective Melted 316L Stainless Steel in Sulphuric Acid Containing Chloride Ion Solution
The open-circuit potential,electrochemical impedance spectroscopy,potentiodynamic po-larization,potentiostats polarization,current-time transient measurements,Mott-Schottky analysis,X-ray photoelectron spectroscopy(XPS),Electron Back-Scattered Diffraction(EBSD)methods were used to in-vestigate the passivation behavior of 316L stainless steel fabricated by laser selective melted(SLM 316L)in 0.05 mol/L H2SO4+0.2 mol/L NaCl solution.The results were compared with commercial rolled 316L stainless steel(R 316L).The results showed that the nucleation of passivation film follows continuous mechanism for the both stainless steel.However,the SLM 316L stainless steel has smaller grain size and higher grain boundary density than those of R 316L stainless steel.Therefore,the grow rate of pas-sivation film is fast.The SLM 316L stainless steel took place transpassivation dissolution,while R 316L stainless steel took place pitting corrosion.The SLM 316L stainless steel has better corrosion resistance.The main reasons are the SLM 316L stainless steel has much more low angle grain boundaries without ferrite.Moreover,the passivation film of SLM 316L stainless steel has lower carrier density,lower ratio of O2-/OH-,lower content of NiO and higher content of Cr2O3 compared with R 316L stainless steel.
materials failure and protectionpassivation behaviorelectrochemical tests316L stain-less steel
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维普
