Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy
Oxide films produced from plasma electrolytic oxidation are porous in structure. While they have some passivating effect in Mg alloys, the pores still lead to corrosion over long periods of exposure. In this study, spray pyrolysis was used to seal the porous oxide layer developed through the plasma...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-10-01
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| Series: | Surfaces |
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| Online Access: | https://www.mdpi.com/2571-9637/6/4/26 |
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| author | Ashish Kumar Singh Reinis Drunka Paula Iesalniece Ilmars Blumbergs Ints Steins Toms-Valdemars Eiduks Mairis Iesalnieks Konstantins Savkovs |
| author_facet | Ashish Kumar Singh Reinis Drunka Paula Iesalniece Ilmars Blumbergs Ints Steins Toms-Valdemars Eiduks Mairis Iesalnieks Konstantins Savkovs |
| author_sort | Ashish Kumar Singh |
| collection | DOAJ |
| description | Oxide films produced from plasma electrolytic oxidation are porous in structure. While they have some passivating effect in Mg alloys, the pores still lead to corrosion over long periods of exposure. In this study, spray pyrolysis was used to seal the porous oxide layer developed through the plasma electrolytic oxidation method on Mg alloy AZ31. The PEO coating acted as a good base for the application of spray pyrolysis due to its morphology. Three different kinds of coatings were obtained using different precursors: zinc acetate for ZnO, phosphoric acid for phosphate (P), and a mixture of zinc acetate and sodium phosphate for ZnO+P. The corrosion performance of all three coatings was studied by performing electrochemical impedance and polarization tests on the samples. Mass loss over a duration of 1 week was measured in 3% NaCl solution using immersion gravimetry. The coating with only phosphate (P) was found to be most corrosion-resistant with 52 times lower rate of corrosion and 50 times more polarization potential. The chemical composition of the corrosion products was studied using XRD and SEM-EDS analysis. Mass loss in ZnO+P was the highest, at up to 1.4 and 5.1 times higher than ZnO and P, respectively. |
| first_indexed | 2024-03-08T20:21:09Z |
| format | Article |
| id | doaj.art-8da056ab345e46b1901bac1660ba703e |
| institution | Directory Open Access Journal |
| issn | 2571-9637 |
| language | English |
| last_indexed | 2024-03-08T20:21:09Z |
| publishDate | 2023-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Surfaces |
| spelling | doaj.art-8da056ab345e46b1901bac1660ba703e2023-12-22T14:43:25ZengMDPI AGSurfaces2571-96372023-10-016436437910.3390/surfaces6040026Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg AlloyAshish Kumar Singh0Reinis Drunka1Paula Iesalniece2Ilmars Blumbergs3Ints Steins4Toms-Valdemars Eiduks5Mairis Iesalnieks6Konstantins Savkovs7SMW Group, Kr. Barona Street 3-1, 1050 Riga, LatviaSMW Group, Kr. Barona Street 3-1, 1050 Riga, LatviaSMW Group, Kr. Barona Street 3-1, 1050 Riga, LatviaFaculty of Mechanical Engineering, Transport and Aeronautics, Institute of Aeronautics, Riga Technical University, 6B Kīpsalas Street Riga, LV-1048 Riga, LatviaSMW Group, Kr. Barona Street 3-1, 1050 Riga, LatviaInstitute of Materials and Surface Engineering, Faculty of Applied Chemistry and Materials Science, Riga Technical University, Ķipsalas Street 6B, 1050 Riga, LatviaInstitute of Materials and Surface Engineering, Faculty of Applied Chemistry and Materials Science, Riga Technical University, Ķipsalas Street 6B, 1050 Riga, LatviaSMW Group, Kr. Barona Street 3-1, 1050 Riga, LatviaOxide films produced from plasma electrolytic oxidation are porous in structure. While they have some passivating effect in Mg alloys, the pores still lead to corrosion over long periods of exposure. In this study, spray pyrolysis was used to seal the porous oxide layer developed through the plasma electrolytic oxidation method on Mg alloy AZ31. The PEO coating acted as a good base for the application of spray pyrolysis due to its morphology. Three different kinds of coatings were obtained using different precursors: zinc acetate for ZnO, phosphoric acid for phosphate (P), and a mixture of zinc acetate and sodium phosphate for ZnO+P. The corrosion performance of all three coatings was studied by performing electrochemical impedance and polarization tests on the samples. Mass loss over a duration of 1 week was measured in 3% NaCl solution using immersion gravimetry. The coating with only phosphate (P) was found to be most corrosion-resistant with 52 times lower rate of corrosion and 50 times more polarization potential. The chemical composition of the corrosion products was studied using XRD and SEM-EDS analysis. Mass loss in ZnO+P was the highest, at up to 1.4 and 5.1 times higher than ZnO and P, respectively.https://www.mdpi.com/2571-9637/6/4/26magnesium alloyZnO–MgOelectrochemical impedance spectroscopyspray pyrolysispotentiodynamic polarization |
| spellingShingle | Ashish Kumar Singh Reinis Drunka Paula Iesalniece Ilmars Blumbergs Ints Steins Toms-Valdemars Eiduks Mairis Iesalnieks Konstantins Savkovs Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy Surfaces magnesium alloy ZnO–MgO electrochemical impedance spectroscopy spray pyrolysis potentiodynamic polarization |
| title | Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy |
| title_full | Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy |
| title_fullStr | Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy |
| title_full_unstemmed | Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy |
| title_short | Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy |
| title_sort | combined peo and spray pyrolysis coatings of phosphate and zno for enhancing corrosion resistance in az31 mg alloy |
| topic | magnesium alloy ZnO–MgO electrochemical impedance spectroscopy spray pyrolysis potentiodynamic polarization |
| url | https://www.mdpi.com/2571-9637/6/4/26 |
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