A Study on the Corrosion Behavior of Magnesium Alloy Sealed with Chemical Conversion Coating and Sol-gel Coating
2
조회
0
다운로드
0
인용
0
참고문헌
키워드
초록
Magnesium alloy is limited in the industrial field because its standard electrode potential is –2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 oC. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 oC in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.
Abstract
Magnesium alloy is limited in the industrial field because its standard electrode potential is –2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 oC. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 oC in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.
참고문헌 (15)
- Dong Han, "A review on ignition mechanisms and characteristics of magnesium alloys", Journal of Magnesium and Alloys, 8(2), pp.329~344 (2020), Elsevier BV[DOI]
- William J. Joost, "Towards magnesium alloys for high-volume automotive applications", Scripta Materialia, 128, pp.107~112 (2017), Elsevier BV[DOI]
- Mark Easton, "Magnesium alloy applications in automotive structures", JOM, 60(11), pp.57~62 (2008), Springer Science and Business Media LLC[DOI]
- Wei Gan, "WITHDRAWN: Study on surface modification and properties of the AZ91D magnesium alloy used for automobile engine", Journal of Materials Research and Technology (2020), Elsevier BV[DOI]
- G. Song, "Corrosion of magnesium alloys in commercial engine coolants", Materials and Corrosion, 56(1), pp.15~23 (2005), Wiley[DOI]
- Peng Zhou, "Revisiting the cracking of chemical conversion coating on magnesium alloys", Corrosion Science, 178, pp.109069~ (2021), Elsevier BV[DOI]
- Shangju Liao, "New design principles for the bath towards chromate- and crack-free conversion coatings on magnesium alloys", Journal of Magnesium and Alloys, 9(2), pp.505~519 (2021), Elsevier BV[DOI]
- Dinesh Balgude, "Sol–gel derived hybrid coatings as an environment friendly surface treatment for corrosion protection of metals and their alloys", Journal of Sol-Gel Science and Technology, 64(1), pp.124~134 (2012), Springer Science and Business Media LLC[DOI]
- J. Mosa, "Active corrosion inhibition of mild steel by environmentally-friendly Ce-doped organic–inorganic sol–gel coatings", RSC Advances, 6(46), pp.39577~39586 (2016), Royal Society of Chemistry (RSC)[DOI]
- M. L. Zheludkevich, "Sol–gel coatings for corrosion protection of metals", Journal of Materials Chemistry, 15(48), pp.5099~ (2005), Royal Society of Chemistry (RSC)[DOI]
- M. Whelan, "Sol–gel sealing characteristics for corrosion resistance of anodised aluminium", Surface and Coatings Technology, 235, pp.86~96 (2013), Elsevier BV[DOI]
- V.R. Capelossi, "Corrosion protection of clad 2024 aluminum alloy anodized in tartaric-sulfuric acid bath and protected with hybrid sol–gel coating", Electrochimica Acta, 124, pp.69~79 (2014), Elsevier BV[DOI]
- Junying Hu, "Composite anticorrosion coatings for AZ91D magnesium alloy with molybdate conversion coating and silicon sol–gel coatings", Progress in Organic Coatings, 66(3), pp.199~205 (2009), Elsevier BV[DOI]
- FLORIAN MANSFELD, "Tafel Slopes and Corrosion Rates from Polarization Resistance Measurements", Corrosion, 29(10), pp.397~402 (1973), Association for Materials Protection and Performance (AMPP)[DOI]
- R. Bandy, "The simultaneous determination of tafel constants and corrosion rate—a new method", Corrosion Science, 20(8-9), pp.1017~1028 (1980), Elsevier BV[DOI]