NH4F가 첨가된 0.5 M 옥살산 전처리가 AZ91 마그네슘 합금의 PEO 피막 형성에 미치는 영향
Effect of pre-treatment in 0.5 M oxalic acid containing various NH4F concentrations on PEO Film Formation of AZ91 Mg Alloy
1
조회
0
다운로드
0
인용
0
참고문헌
키워드
초록
This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C2H2O4) solution containing various ammonium fluoride (NH4F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm2 of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na2SiO3 solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH4F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH4F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH4F more than 0. 3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.
Abstract
This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C2H2O4) solution containing various ammonium fluoride (NH4F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm2 of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na2SiO3 solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH4F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH4F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH4F more than 0. 3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.
참고문헌 (9)
- C. Blawert, "Anodizing Treatments for Magnesium Alloys and Their Effect on Corrosion Resistance in Various Environments", Adv. Eng. Mater, 8, pp.511~533 (2006)
- R. D. Arrabal, "Corrosion behaviour of a magnesium matrix composite with a silicate plasma electrolytic oxidation coating", Corros. Sci, 52, pp.3738~3749 (2010)
- 문성모, "AZ31 Mg합금의 PEO피막 형성거동에 미치는 인산나트륨 농도의 영향", 한국표면공학회지, 52(5), pp.265~274 (2019), 한국표면공학회[DOI]
- S V Satya Prasad, "The role and significance of Magnesium in modern day research-A review", Journal of Magnesium and Alloys, 10(1), pp.1~61 (2022), Elsevier BV[DOI]
- Y. Yang, "Research advances in magnesium and magnesium alloys worldwide in 2020", J. Magnes. Alloy, 9, pp.705~747 (2021)
- A. Pardo, "Corrosion behaviour of magnesium", aluminium alloys in 3.5wt.%NaCl, 2008, pp.50, 823~834
- Z. Shi, "Corrosion resistance of anodised single-phase Mg alloys", Surf. Coat. Technol, 201, pp.492~503 (2006)
- R. Arrabal, "Corrosion resistance of WE43 and AZ91D magnesium alloys with phosphate PEO coatings", Corros. Sci, 50, pp.1744~1752 (2008)
- 권두영, "AZ91 마그네슘 합금의 PEO 피막 형성거동에 미치는 HF전처리의 영향", 한국표면공학회지, 54(4), pp.184~193 (2021), 한국표면공학회