Research on the Mechanism of Electrochemically Induced Surface Annealing in Stainless Steel and Improvement of the Technique
|School||Beijing University of Chemical Technology|
|Course||Materials Science and Engineering|
|Keywords||Electrochemically induced annealing Stainless steel Hydrogen Cathode / anode time pH value Deal with media Corrosion resistance|
Electrochemically induced annealing (Electrochemically Induced Surface Annealing, EISA) is positive and negative alternating pulse processing a metastable austenitic stainless steel to improve its corrosion resistance . Since the phenomenon is found for its mechanism has never stopped , but it has not come to a definitive conclusion , and a single processing medium sodium nitrite limit the actual engineering of the process , the liquid waste treatment will lead to environmental pollution . This article by cathode hydrogen charging method of observation to the course of the reaction of hydrogen in the process of EISA , show that the hydrogen to penetrate into the surface layer of the stainless steel cathode in the electrical pulse stage and the anode phase is re-oxidized back to the processing medium , partially confirmed Burstein et al hypotheses about the the phenomenon mechanism of EISA . Also studied the influence of the cathode / anode time , pH of the medium , the cathode potential , and other factors on the EISA treatment effect , determine the long the cathode / short anode electric pulse processing method , the phase change of the processing time is shorter than the three hours the EISA , improve the processing efficiency . In addition, different medium stainless steel processing of positive and negative alternating pulses of XRD , metallographic observation , cyclic voltammetry , potentiodynamic scanning the organization before and after the change in the method of processing , corrosion resistance change mechanism, the results show that : the EISA phase change medium can be other than the sodium nitrite , such as sodium carbonate solution , nitrogen does not occur EISA phase change necessary conditions . Sodium carbonate in the EISA phase transition can also reduce the sensitivity of the pitting corrosion of stainless steel in NaCl solution ; the electrical pulse processing sodium sulfite , sodium silicate , sodium acetate and sodium hydroxide solution easily lead to martensite is priority corrosion .