A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy
This study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study...
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MDPI AG
2022-05-01
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author | Chun-Wei Chen Salim Levent Aktug Chin-Jou Chang Yueh-Lien Lee Ming-Der Ger Shun-Yi Jian |
author_facet | Chun-Wei Chen Salim Levent Aktug Chin-Jou Chang Yueh-Lien Lee Ming-Der Ger Shun-Yi Jian |
author_sort | Chun-Wei Chen |
collection | DOAJ |
description | This study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study uses acid pickling instead of mechanical grinding, and a nitric acid solution is used for pickling. After pretreatments, the samples are immersed for 30 s in a conversion coating solution containing 0.1 M KMnO<sub>4</sub> and 0.025 M Ce(NO<sub>3</sub>)<sub>3</sub> with a pH of 1.5, as demonstrated in previous studies by the authors. The microstructure of the coating layer and electrochemical behavior of conversion coated samples exposed to 3.5 wt.% NaCl solution are studied. The corrosion behavior of Mn-Ce conversion coating specimens is determined using a salt spray test (SST). Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) are used to analyze the interface between the coating layer and the underlying magnesium substrate and to investigate the microstructure of the specimens. The roughness of the coatings is measured using 3D white light interferometry. The results show that the deteriorated area ratio for conversion coated LZ91 decreases to less than 5% after 72 h of SST exposure, and the corrosion resistance is improved 2.25 times with the Mn-Ce conversion coating on LZ91 magnesium alloy. |
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spelling | doaj.art-dfb430b33fbb4f5cadd5c879352bedde2023-11-23T08:56:54ZengMDPI AGNanomaterials2079-49912022-05-01129161410.3390/nano12091614A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium AlloyChun-Wei Chen0Salim Levent Aktug1Chin-Jou Chang2Yueh-Lien Lee3Ming-Der Ger4Shun-Yi Jian5Department of Chemical & Materials Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, TaiwanDepartment of Materials Science and Engineering, Gebze Technical University, Gebze 41400, Kocaeli, TurkeyDepartment of Chemical & Materials Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, TaiwanDepartment of Engineering Science and Ocean Engineering, National Taiwan University, Taipei 10617, TaiwanDepartment of Chemical & Materials Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, TaiwanDepartment of Material Engineering, Ming Chi University of Technology, New Taipei City 24301, TaiwanThis study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study uses acid pickling instead of mechanical grinding, and a nitric acid solution is used for pickling. After pretreatments, the samples are immersed for 30 s in a conversion coating solution containing 0.1 M KMnO<sub>4</sub> and 0.025 M Ce(NO<sub>3</sub>)<sub>3</sub> with a pH of 1.5, as demonstrated in previous studies by the authors. The microstructure of the coating layer and electrochemical behavior of conversion coated samples exposed to 3.5 wt.% NaCl solution are studied. The corrosion behavior of Mn-Ce conversion coating specimens is determined using a salt spray test (SST). Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) are used to analyze the interface between the coating layer and the underlying magnesium substrate and to investigate the microstructure of the specimens. The roughness of the coatings is measured using 3D white light interferometry. The results show that the deteriorated area ratio for conversion coated LZ91 decreases to less than 5% after 72 h of SST exposure, and the corrosion resistance is improved 2.25 times with the Mn-Ce conversion coating on LZ91 magnesium alloy.https://www.mdpi.com/2079-4991/12/9/1614LZ91 magnesium alloyacid pickling pretreatmentconversion coatingmicrostructurecorrosion resistance |
spellingShingle | Chun-Wei Chen Salim Levent Aktug Chin-Jou Chang Yueh-Lien Lee Ming-Der Ger Shun-Yi Jian A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy Nanomaterials LZ91 magnesium alloy acid pickling pretreatment conversion coating microstructure corrosion resistance |
title | A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy |
title_full | A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy |
title_fullStr | A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy |
title_full_unstemmed | A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy |
title_short | A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy |
title_sort | chromate free and convenient route to fabricate thin and compact conversion coating for corrosion protection on lz91 magnesium alloy |
topic | LZ91 magnesium alloy acid pickling pretreatment conversion coating microstructure corrosion resistance |
url | https://www.mdpi.com/2079-4991/12/9/1614 |
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