Corrosion resistance of cerium conversion film electrodeposited on Mg-Gd-Y-Zr magnesium alloy

Abstract

The cerium conversion film was applied to improving the corrosion resistance of Mg-Gd-Y-Zr magnesium alloy. The film was electrodeposited on the surface of the Mg-RE alloy in cerium nitrate solution. The compositions and morphologies were analyzed by X-ray diffraction(XRD), scanning election microscopy (SEM). The corrosion behaviors of the film were investigated electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests and immersion tests. The results show that the optimum parameters for electrochemical deposition are as follows: pH 10.0, time 30 min, 50 mmol/L Na₂CO₃ and temperature 25 °C by the designed experiments according to the orthogonal table L(9, 3⁴). The corrosion protection efficiency is dependent on the deposition parameters. The cerium conversion film shows better corrosion protection behavior than chromate conversion film on Mg-Gd-Y-Zr magnesium alloy.

Keywords

Mg-Gd-Y-Zr magnesium alloy / conversion film / corrosion

References

[1] Winston RevieR., UhligH. H.Corrosion and corrosion controll [M], 20084th edHoboken, John Wiley & Sons Inc: 399

[2] XiaoY., ZhangX.-m., ChenJ.-m., JiangH.. Microstructures and mechanical properties of Mg-15Gd-0.6Zr alloy [J]. The Chinese Journal of Nonferrous Metals, 2006, 16(4): 709-714

[3] Ben-HamuG., EliezerD., ShinK. S., CohenS.. The relation between microstructure and corrosion behavior of Mg-Y-RE-Zr alloys [J]. Alloys and Compounds, 2007, 431: 269-276

[4] GaoY., WangQ.-d., GuJ.-h., ZhaoY., TongY.. Behavior of Mg-15Gd-5Y-0.5Zr alloy during solution heat treatment from 500 to 540 °C [J]. Materials Science and Engineering A, 2007, A459: 117-123

[5] PincW., GengS., O’KeefeM., FahrenholtzW., O’KeefeT.. Effects of acid and alkaline based surface preparation on spray deposited cerium based conversion coatings on Al2024-T3[J]. Applied Surface Science, 2009, 255: 4061-4065

[6] ZhaoM., WuS. S., AnP., FukudaY., NakaeH.. Growth of multi-elements complex coatings on AZ91D magnesium alloy through conversion treatment [J]. Alloys and Compounds, 2007, 427: 310-315

[7] RuddA. L., BreslinC. B., MansfeldF.. The corrosion protection afforded by rare earth conversion coatings applied to magnesium [J]. Corrosion Science, 2000, 42: 275-288

[8] DabalaM., BrunelliK., EnricoN., MaurizioM.. Cerium chemical conversion coatings on AZ63 magnesium alloy [J]. Surface Coating Technology, 2003, 172: 227-232

[9] YiJ.-l., ZhangX.-m., ChenM.-a., GuR.. Effect of Na2CO3 on corrosion resistance of cerium conversion film on Mg-Gd-Y-Zr magnesium alloys [J]. Scripta Materialia, 2008, 59: 955-958

[10] BonoraP. L., AndreiM., EliezerA., GutmanE. M.. Corrosion behaviour of stressed magnesium alloys [J]. Corrosion Science, 2002, 44: 729-749

[11] XuanL., OkeefeT. J., StofferJ. O.An environmentally compliant cerium conversion coating for aluminum protection [D], 1998, Rolla, University of Missouri-Rolla

[12] SongG., AtrensA., StjohnD., NairnJ., LiY.. The electrochemical corrosion of pure magnesium in 1 N NaCl [J]. Corrosion Science, 1997, 39(5): 855-875

[13] MontemorM. F., SimoesA. M., CarmeM. J.. Characterization of rare-earth conversion film formed on the AZ31 magnesium alloy and its relation with corrosion protection [J]. Applied Surface Science, 2007, 253: 6922-6931

[14] ArdeleanH., FiaudC., MarcusP.. Enhanced corrosion resistance of magnesium and its alloys through the formation of cerium (and aluminium) oxide surface film [J]. Materials and Corrosion, 2001, 52: 889-895

[15] BrunelliK., DabalaM., CalliariI., MagriniM.. Effect of HCl pre-treatment on corrosion resistance of cerium-based conversion coatings on magnesium and magnesium alloys [J]. Corrosion Science, 2005, 47: 989-1000