Influence of surface etching pretreatment on PEO process of eutectic Al-Si alloy

doi:10.1016/j.cjche.2015.06.004

Abstract

Abstract: To solve the problems generally encountered during the plasma electrolytic oxidation (PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over thewhole process. The difference between the positive voltages of non-etched and etched specimens decreases graduallywith the increase of processing time. The pretreatment exhibitsmuch less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min^-1 and the energy consumption is decreased from 6.30 to 4.36 kW·h·μm^-1·m^-2. At the same time, both mullite and amorphous SiO₂ contents are decreased in the coating.

Key words: Plasma electrolytic oxidation, Eutectic Al-Si alloy, Pretreatment, Etching

摘要： To solve the problems generally encountered during the plasma electrolytic oxidation (PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over thewhole process. The difference between the positive voltages of non-etched and etched specimens decreases graduallywith the increase of processing time. The pretreatment exhibitsmuch less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min^-1 and the energy consumption is decreased from 6.30 to 4.36 kW·h·μm^-1·m^-2. At the same time, both mullite and amorphous SiO₂ contents are decreased in the coating.

关键词: Plasma electrolytic oxidation, Eutectic Al-Si alloy, Pretreatment, Etching

Kang Li, Wenfang Li, Guoge Zhang, Min Wang, Peng Tang. Influence of surface etching pretreatment on PEO process of eutectic Al-Si alloy[J]. , 2015, 23(9): 1572-1578.

References

[1] O. Uzun, T. Karaaslan, M. Gogebakan, M. Keskin, Hardness and microstructural characteristics of rapidly solidified Al-8-16wt% Si alloys, J. Alloys Compd. 376 (2004) 149-157.
[2] B.K. Prasad, K. Venkateswarlu, O.P. Modi, A.K. Jha, S. DAS, R. Dasgupta, A.H. Yegneswaran, Sliding wear behavior of some Al-Si alloys: Role of shape and size of Si particles and test conditions, Metall. Mater. Trans. A 29 (1998) 2747-2752.
[3] X. Li, X. Nie, L. Wang, D.O. Northwood, Corrosion protection properties of anodic oxide coatings on an Al-Si alloy, Surf. Coat. Technol. 200 (2005) 1994-2000.
[4] A. Forn, J.A. Picas, M.T. Baile, E. Martin, V.G. García, Microstructure and tribological properties of anodic oxide layer formed on Al-Si alloy produced by semisolid processing, Surf. Coat. Technol. 202 (2007) 1139-1143.
[5] K.V. Ashok, Sparking voltages and side reactions during anodization of valve metals in terms of electron tunnelling, Corros. Sci. 11 (1971) 411-417.
[6] F.C.Walsh, C.T.J. Low, R.J.K.Wood, K.T. Stevens, J. Archer, A.R. Poeton, A. Ryder, Plasma electrolytic oxidation (PEO) for production of anodised coatings on lightweight metal (Al, Mg, Ti) alloys, Trans. Inst. Met. Finish. 87 (2009) 122-135.
[7] R.C. Barik, J.A. Wharton, R.J.K. Wood, K.R. Stokes, R.L. Jones, Corrosion, erosion and erosion-corrosion performance of plasma electrolytic oxidation (PEO) deposited Al₂O₃ coatings, Surf. Coat. Technol. 199 (2005) 158-167.
[8] J.A. Curran, H. Kalkanc, Y. Magurova, T.W. Clyne, Mullite-rich plasma electrolytic oxide coatings for thermal barrier applications, Surf. Coat. Technol. 201 (2007) 8683-8687.
[9] W.B. Xue, X.L. Shi, M. Hua, Y.L. Li, Preparation of anti-corrosion films by micro arc oxidation on an Al-Si alloy, Appl. Surf. Sci. 253 (2007) 6118-6124.
[10] L. Wang, X. Nie, Silicon effects on formation of EPO oxide coatings on aluminum alloys, Thin Solid Films 494 (2006) 211-218.
[11] L.R. Krishna, A.S. Purnima, N.P.Wasekar, G. Sundararajan, Kinetics and properties of micro arc oxidation coatings deposited on commercial Al alloys, Metall.Mater. Trans. A 38 (2007) 370-378.
[12] E. Matykina, R. Arrabal, P. Skeldon, G.E. Thompson, Optimisation of the plasma electrolytic oxidation process efficiency on aluminium, Surf. Interface Anal. 42 (2010) 221-226.
[13] A.L. Yerokhin, A. Leyland, A. Matthews, Kinetic aspects of aluminium titanate layer formation on titanium alloys by plasma electrolytic oxidation, Appl. Surf. Sci. 200 (2002) 172-184.
[14] C.R. Eritzsche, Anodic growth, dielectric breakdown and carrier transport in amorphous SiO₂ films, J. Phys. Chem. Solids 30 (1969) 1885-1895.
[15] Q.B. Li, J. Liang, B.X. Liu, Z.J. Peng, Q. Wang, Effects of cathodic voltages on structure and wear resistance of plasma electrolytic oxidation coatings formed on aluminium alloy, Appl. Surf. Sci. 297 (2014) 176-181.
[16] M.Q. Tang,W.P. Li, H.C. Liu, L.Q. Zhu, Influence of K2TiF6 in electrolyte on characteristics of the microarc oxidation coating on aluminum alloy, Curr. Appl. Phys. 12 (2012) 1259-1265.
[17] A.L. Yerokhin, T.A. Shatrov, V. Samsonov, P. Shashkov, A. Pilkington, A. Leyland, A. Matthews, Oxide ceramic coatings on aluminium alloys produced by a pulsed bipolar plasma electrolytic oxidation process, Surf. Coat. Technol. 199 (2005) 150-157.
[18] D.J. Shen, J. Zou, L.L. Wu, F.F. Liu, G.L. Li, J.R. Cai, D.L. He, H.J. Ma, G.R. Jiang, Microstructure and corrosion behavior of micro-arc oxidation coating on 6061 aluminum alloy pre-treated by high-temperature oxidation, Appl. Surf. Sci. 265 (2013) 431-437.
[19] E.S. Kooij, K. Butter, J.J. Kelly, Silicon etching in HNO3/HF solution: Charge balance for the oxidation reaction, Electrochem. Solid-State Lett. 2 (4) (1999) 178-180.
[20] C. Rallan, A. Garforth, Growth of hierarchically structured high-surface area alumina on FeCralloy® rods, Chin. J. Chem. Eng. 22 (2014) 861-868.
[21] F.M. Alkharafi, W.A. Badawy, Corrosion and passivation of Al and Al-Si alloys in nitric acid solutions II—effect of chloride ions, Electrochim. Acta 40 (1995) 1811-1817.
[22] J.W. Schultze, M.M. Lohrengel, Stability, reactivity and breakdown of passive films: Problems of recent and future research, Electrochim. Acta 45 (2000) 2499-2513.
[23] F.T. Xu, Y. Xia, G. Li, Themechanismof PEO process on Al-Si alloys with the bulk primary silicon, Appl. Surf. Sci. 255 (2009) 9531-9538.
[24] R.O. Hussein, X. Nie, D.O. Northwood, A. Yerokhin, A.Matthews, Spectroscopic study of electrolytic plasma and discharging behaviour during the plasma electrolytic oxidation (PEO) process, J. Phys. D. Appl. Phys. 43 (2010) 1-16.
[25] A.L. Yerokhin, L.O. Snizhko, N.L. Gurevina, A. Leyland, A. Pilkington, A. Matthews, Discharge characterization in plasma electrolytic oxidation of aluminium, J. Phys. D. Appl. Phys. 36 (2003) 2110-2120.
[26] A.A. Voevodin, A.L. Yerokhin, V.V. Lyubimov, M.S. Donley, J.S. Zabinski, Characterization of wear protective Al-Si-O coatings formed on Al-based alloys by micro-arc discharge treatment, Surf. Coat. Technol. 86-87 (1996) 516-521.