{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T05:15:01Z","timestamp":1790054101645,"version":"4.0.1"},"reference-count":32,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T00:00:00Z","timestamp":1783036800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Aiming at non-uniformity in the vertical direction in the polishing effect on stainless steel after plasma electrolytic polishing (PEP), this paper took 304 L stainless steel as the research object. Under an ammonium sulfate electrolyte system with a mass fraction of 2.5 wt%, PEP was carried out utilizing different placement methods for the anode and electrolyte temperatures, and the causes of non-uniformity in the polishing process were explored. Experimental results demonstrate that the vertical polishing inhomogeneity originates from the upward movement of unruptured bubbles at the sample bottom. Under the combined effects of electrolyte internal pressure and bubble buoyancy, a vapor-gas envelope (VGE) featuring a thick upper part and thin lower part forms near the sample surface. This enhances plasma-related physicochemical reactions at the sample bottom and consequently raises the polishing rate. The vertical polishing unevenness can be alleviated by adjusting the electrolyte temperature. Non-uniformity could be improved by controlling the temperature of the electrolyte. Compared with the result at 95 \u00b0C, the maximum dimensional variation in each region on the sample at 75 \u00b0C was reduced by 36% because a VGE with more uniform thickness was formed, and a properly oxidized sparse layer helped protect the substrate from ablation and over-polishing. In addition, the removal rate of elements on the surface of stainless steel is affected by its activity due to the oxidation reaction. The high removal amount in the bottom region caused a trend of increasing Cr and decreasing Fe content percentages from the top to the bottom on the stainless-steel surface. However, the oxidation removal rate of elements is extremely fast due to the high temperature of the ionization center and strong electric field; therefore, the content percentage of each element on the surface is little changed after polishing.<\/jats:p>","DOI":"10.3390\/ma19132849","type":"journal-article","created":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T14:33:06Z","timestamp":1783089186000},"page":"2849","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Study on Vertical Non-Uniformity of Plasma Electrolytic Polishing"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-1821-5862","authenticated-orcid":false,"given":"Ziyuan","family":"Zhu","sequence":"first","affiliation":[{"name":"College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8036-7907","authenticated-orcid":false,"given":"Hongtao","family":"Li","sequence":"additional","affiliation":[{"name":"College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xuchen","family":"Lu","sequence":"additional","affiliation":[{"name":"College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chao","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"537","DOI":"10.3788\/COL20090706.0537","article-title":"New development of atmospheric pressure plasma polishing","volume":"7","author":"Wang","year":"2009","journal-title":"Chin. Opt. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5393","DOI":"10.1007\/s11661-018-4889-4","article-title":"Effect of Ball Burnishing Treatment on the Fatigue Behavior of 316L Stainless Steel Operating Under Anodic and Cathodic Polarization Potentials","volume":"49","author":"Yilmaz","year":"2018","journal-title":"Metall. Mater. Trans."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/j.rcim.2018.07.005","article-title":"Synergistic integrated design of an electrochemical mechanical polishing end-effector for robotic polishing applications","volume":"55","author":"Mohammad","year":"2019","journal-title":"Robot. Comput. Integr. Manuf."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"4805","DOI":"10.1007\/s12206-017-0928-0","article-title":"Parameter optimization of five-axis polishing using abrasive belt flap wheel for blisk blade","volume":"31","author":"Zhang","year":"2017","journal-title":"J. Mech. Sci. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1007\/s10008-021-05037-2","article-title":"Electrochemical polishing versus mechanical polishing of AISI 304: Surface and electrochemical study","volume":"26","author":"Abouelata","year":"2022","journal-title":"J. Solid State Electrochem."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1873","DOI":"10.1007\/s00170-020-06165-1","article-title":"Machine learning\u2013driven in situ process monitoring with vibration frequency spectra for chemical mechanical planarization","volume":"111","author":"Liu","year":"2020","journal-title":"Int. J. Adv. Manuf. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2367","DOI":"10.1007\/s00170-015-7992-3","article-title":"Laser micro-polishing for metallic surface using UV nano-second pulse and CW lasers","volume":"85","author":"Jang","year":"2016","journal-title":"Int. J. Adv. Manuf. Technol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1007\/s00170-019-03559-8","article-title":"Influence of laser spot scanning speed on micro-polishing of metallic surface using UV nanosecond pulse laser","volume":"103","author":"Jang","year":"2019","journal-title":"Int. J. Adv. Manuf. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Zhang, C., Cai, Y., Zhang, H., Li, J., Song, Q., Wang, B., and Liu, Z. (2024). Investigation of Surface Integrity of Conical Hole in Laser Polishing 440C Stainless Steel. Metals, 14.","DOI":"10.3390\/met14010058"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1310","DOI":"10.1016\/j.jmapro.2024.12.028","article-title":"Laser Polishing of Additive Manufactured Stainless-Steel Parts by Line Focused Beam: A Response Surface Method for Improving Surface Finish","volume":"133","author":"Kumar","year":"2025","journal-title":"J. Manuf. Process."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"110152","DOI":"10.1016\/j.triboint.2024.110152","article-title":"Investigations of the Hybrid Laser Polishing and High-Temperature Tribological Properties of the 316L Stainless Steel Formed by Selective Laser Melting","volume":"200","author":"Zhang","year":"2024","journal-title":"Tribol. Int."},{"key":"ref_12","first-page":"1","article-title":"Obtaining tailored surface characteristics by combining shot peening and electropolishing on 316L stainless steel","volume":"492","author":"Vara","year":"2019","journal-title":"Appl. Surf. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/j.surfcoat.2019.07.018","article-title":"Electropolishing of aluminium in a deep eutectic solvent","volume":"375","author":"Kityk","year":"2019","journal-title":"Surf. Coat. Technol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"127631","DOI":"10.1016\/j.matlet.2020.127631","article-title":"The influence of substrate electropolishing on anodization behavior, corrosion resistance, cytocompatibility and antibacterial ability of NiTi alloy","volume":"268","author":"Sun","year":"2020","journal-title":"Mater. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1002\/jemt.23588","article-title":"Twin-jet electropolishing for damage-free transmission electron microscopy specimen preparation of metallic microwires","volume":"84","author":"Pourbabak","year":"2021","journal-title":"Microsc. Res. Tech."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"260","DOI":"10.3934\/matersci.2016.1.260","article-title":"Plasma electrolytic polishing of metalized carbon fibers","volume":"3","author":"Nestler","year":"2016","journal-title":"Aims Mater. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1016\/j.jmapro.2026.02.047","article-title":"On the Brink of Mass Production and Simultaneous Multi-Component Surface Modifications for Ultra-Fast Polishing: Plasma Electrolytic Polishing Process","volume":"164","author":"Bolat","year":"2026","journal-title":"J. Manuf. Process."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"503","DOI":"10.1016\/j.procir.2016.02.240","article-title":"Plasma electrolytic polishing\u2014An overview of applied technologies and current challenges to extend the polishable material range","volume":"42","author":"Nestler","year":"2016","journal-title":"Procedia CIRP"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Stepputat, V.N., Zeidler, H., Safranchik, D., Strokin, E., and Bottger-Hiller, F. (2021). Investigation of Post-Processing of Additively Manufactured Nitinol Smart Springs with Plasma-Electrolytic Polishing. Materials, 14.","DOI":"10.3390\/ma14154093"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"507","DOI":"10.1080\/02670844.2017.1406574","article-title":"Aspects of anodic plasma electrolytic polishing of nitrided steel","volume":"35","author":"Kusmanov","year":"2019","journal-title":"Surf. Eng."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"55","DOI":"10.3103\/S1068375520010032","article-title":"Influence of plasma electrolytic polishing conditions on surface roughness of steel","volume":"56","author":"Belkin","year":"2020","journal-title":"Surf. Eng. Appl. Electrochem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"101404","DOI":"10.1016\/j.ijoes.2026.101404","article-title":"Electrohydrodynamic modeling and experimental study of electrolyte plasma polishing of high-strength steel surfaces","volume":"21","author":"Li","year":"2026","journal-title":"Int. J. Electrochem. Sci."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Cornelsen, M., Deutsch, C., and Seitz, H. (2018). Electrolytic Plasma Polishing of Pipe Inner Surfaces. Metals, 8.","DOI":"10.3390\/met8050330"},{"key":"ref_24","first-page":"1858","article-title":"Electrochemical degradation of metoprolol in aquatic environment over a Ti\/Ti4O7 anode","volume":"38","author":"Zhi","year":"2018","journal-title":"Acta Sci. Circumstantiae"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Wang, J., Suo, L.C., and Fu, Y.L. (2012). Study on material removal rate of electrolysis and plasma polishing. 2012 IEEE International Conference on Information and Automation, IEEE.","DOI":"10.1109\/ICInfA.2012.6246913"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"C184","DOI":"10.1149\/2.0631605jes","article-title":"Self-Organization Kinetics of Microarc Oxidation: Nonequilibrium-State Electrode Reaction Kinetics","volume":"163","author":"Mi","year":"2016","journal-title":"J. Electrochem. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"369","DOI":"10.1016\/j.electacta.2014.01.047","article-title":"Plasma formation mechanism of microarc oxidation","volume":"123","author":"Mi","year":"2014","journal-title":"Electrochim. Acta"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/S0257-8972(99)00441-7","article-title":"Plasma Electrolysis for Surface Engineering","volume":"122","author":"Yerokhin","year":"1999","journal-title":"Surf. Coat. Technol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"296","DOI":"10.1016\/j.electacta.2016.04.186","article-title":"A mechanism for the growth of a plasma electrolytic oxide coating on Al","volume":"208","author":"Zhu","year":"2016","journal-title":"Electrochimica Acta"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"301","DOI":"10.4028\/www.scientific.net\/MSF.532-533.301","article-title":"The Influence of Acoustic Cavitation to Microscopic Material Removal in Polishing Process Based on Vibration of Liquid: A Numerical Study","volume":"51","author":"Guo","year":"2006","journal-title":"Mater. Sci. Forum"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1055","DOI":"10.1002\/maco.201307040","article-title":"Influence of irregularities in the electrolyte on the cathodic protection of steel: A numerical and experimental study","volume":"64","author":"Montoya","year":"2013","journal-title":"Mater. Corros."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"085021","DOI":"10.1088\/1361-6595\/aba4b9","article-title":"Nanosecond pulsed discharges in distilled water-Part II: Line emission and plasma propagation","volume":"29","author":"Keudell","year":"2020","journal-title":"Plasma Sources Sci. Technol."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/13\/2849\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,10]],"date-time":"2026-07-10T04:18:06Z","timestamp":1783657086000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/13\/2849"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,3]]},"references-count":32,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["ma19132849"],"URL":"https:\/\/doi.org\/10.3390\/ma19132849","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,3]]}}}