In general, complete mechanical cleaning and chemical cleaning of magnesium alloys are essential to good coating adhesion and the final corrosion resistance. It is important that special precaution must be taken to avoid sparks during grinding or polishing of magnesium alloys in dry conditions. Owning to the application of current or voltage, anodizing processes usually provide denser and thicker coating structure and therefore better corrosion protection than the performance of chemical conversion coatings. Magnesium anodizing is recommended when a high corrosion resistance is desired, which is the case in many automotive, aerospace, and marine applications. In response to environmental protection laws, chromate minimization policies, and other regulations, chromate-based surface treatments, as specified in current standards of chemical conversion coating and anodizing for Mg, are increasingly restricted. Research efforts have been made to look for alternative processes. The newly developed chromate-free PEO processes are more effective and reliable to achieve better paint adhesion and corrosion resistance.

References

Ardelean H, Frateur I, Marcus P (2008) Corrosion protection of magnesium alloys by cerium, zirconium and niobium-based conversion coatings. Corros Sci 50(7):1907–1918

ASM International (1996) Guide to mechanical cleaning systems. Guide to surface cleaning processes, vol 3. ASM International, Materials Park

ASTM B322 (2003) Practice for cleaning metals prior to electroplating. Annual book of ASTM standards, vol 02.02. ASTM International, Materials Park

ASTM B879 (2003) Standard practices for applying non-electrolytic conversion coatings on magnesium and magnesium alloys. Annual book of ASTM standards, vol 02.02. ASTM International, Materials Park

ASTM B893 (2003) Specification for hard-coat anodizing of magnesium for engineering applications. Annual book of ASTM standards, vol 02.02. ASTM International, Materials Park

ASTM D1732 (2007) Standard practices for preparation of magnesium alloy surfaces for painting. Annual book of ASTM standards, vol 02.02. ASTM International, Materials Park

Atanasyants AG, Nikitin KN (2001) Activation and passivation of zirconium by electrochemical treatment in aqueous and non-aqueous chloride solutions. Russ J Electrochem 37(9):899–906

Avedesian MM, Baker H (1999) ASM specialty handbook: magnesium and magnesium alloys, vol 274. ASM international, Materials Park

Bai LQ, Li D (2004) New development of anodizing process of magnesium alloys. Trans Nonfer Metal Soc China 14:120–125

Banerjee PC, Raman RKS (2011) Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41. Electrochim Acta 56(11):3790–3798

Bartak DE, Lemieux BE, Woolsey ER (1993a) Two-step chemical/electrochemical process for coating magnesium alloys. US Patent 5,240,589

Bartak DE, Lemieux BE, Woolsey ER (1993b) Two-step electrochemical process for coating magnesium alloys. US Patent 5,264,113

Bartak DE, Lemieux BE, Woolsey ER (1993c) Coated magnesium alloys. US Patent 5,266,412

Bartak DE, Lemieux BE, Woolsey ER (1995) Hard anodic coating for magnesium alloys. US Patent 5,470,664

Barton TF, Macculloch JA, Ross PN (2001) Anodization of magnesium and magnesium based alloys. US Patent 6,280,598

Basaly MA, Massad SK, Agudelo LF (1995) Process and composition for sealing anodized aluminum surfaces. US Patent 5,411,607

Blawert C et al (2006) Anodizing treatments for magnesium alloys and their effect on corrosion resistance in various environments. Adv Eng Mater 8(6):511–533

Budiloff N (1942) Method for manufacturing hard and compact protective layers on magnesium and magnesium alloys. US Patent 2,305,669

Buzzard RW (1943) Method of and bath for coating magnesium. US Patent 2,314,341

Chen XB, Birbilis N, Abbott TB (2011) Review of corrosion-resistant conversion coatings for magnesium and its alloys. Corrosion 67(3):035005

Chen MA, Huang R, Lu XB (2011) Corrosion protection of AZ31 magnesium alloy by silane film of partly hydrolysed BTESPT. Corros Eng Sci Technol 46(6):712–718

Chong KZ, Shih TS (2003) Conversion-coating treatment for magnesium alloys by a permanganate-phosphate solution. Mater Chem Phys 80(1):191–200

Cormier GJ (2005) Alkaline cleaning. In: ASM handbook

Costa M (1997) Toxicity and carcinogenicity of Cr(VI) in animal models and humans. Crit Rev Toxicol 27(5):431–442

Costa M, Klein CB (2006) Toxicity and carcinogenicity of chromium compounds in humans. Crit Rev Toxicol 36(2):155–163

Dickman AJ (2011) The science of scratches – polishing and buffing mechanical surface preparation. In: Tucker RE (ed) Metal finishing surface finishing guidebook. Valero, G. Elsevier, New York, USA

Dolan SE (2004) Light metal anodization. US Patent 6,797,147

Dolan SE (2005) Light metal anodization. US Patent 6,916,414

Evangelides HA (1955) Method of electrolytically coating magnesium and electrolyte therefore. US Patent 2,723,952

Evangelides HA (1959) Method and bath for electrolytically coating magnesium. US Patent 2,880,148

Fahrenholtz WG et al (2002) Characterization of cerium-based conversion coatings for corrosion protection of aluminum alloys. Surf Coat Technol 155(2–3):208–213

Friedrich HE, Mordike BL (2006) Magnesium technology: metallurgy, design data, applications. Springer, New York

Gray JE, Luan B (2002) Protective coatings on magnesium and its alloys – a critical review. J Alloys Compd 336(1–2):88–113

Hawkins JH (1993) Assessment of protective finishing systems for magnesium. In: Proceedings of the annual world magnesium conference. International Magnesium Association. Washington DC, USA

Herbert K (1959) Anodizing magnesium. US Patent 2,901,409

Herbert D (2011) Blast finishing. In: Tucker RE (ed) Metal finishing surface finishing guidebook. Valero, G. Elsevier, New York, USA

Hillis JE (2005) Surface engineering of magnesium alloys. In: Faith Reidenbach (ed) ASM handbook ASM International ASM World Headquarters, OH, USA.

Hu JY et al (2009) Composite anticorrosion coatings for AZ91D magnesium alloy with molybdate conversion coating and silicon sol-gel coatings. Prog Org Coat 66(3):199–205

Hu JY et al (2010) Organic coatings silane-based for AZ91D magnesium alloy. Thin Solid Films 519(4):1361–1366

Hudson RM (2005) Pickling and descaling. In: ASM handbook

ISO 27831-2:2008 (2008) Metallic and other inorganic coatings – cleaning and preparation of metal surfaces – part 2: non-ferrous metals and alloys International Organization for Standardization ISO. Geneva, Switzerland

Jenny A (1933) Production of anticorrosive protective coatings on light metals. US 1,923,539

Kainer KU, Kaiser F (2003) Magnesium alloys and technology. Wiley Online Library, Weinheim

Keelee LJ (1926) Protective coating for magnesium. US Patent 1,574,289

Kendig M, Jeanjaquet S (2002) Cr(VI) and Ce(III) inhibition of oxygen reduction on copper. J Electrochem Soc 149(2):B47–B51

Kobayashi W, Uehori K, Furuta M (1988) Anodizing solution for anodic oxidation of magnesium or its alloys. US Patent 4,744,872

Kostilnik T (2005) Mechanical cleaning systems. In: ASM handbook

Lamaka S et al (2008) Novel hybrid sol-gel coatings for corrosion protection of AZ31B magnesium alloy. Electrochim Acta 53(14):4773–4783

Li LJ et al (2008) Formation and characterization of cerium conversion coatings on magnesium alloy. J Rare Earth 26(3):383–387

Lin CS, Fang SK (2005) Formation of cerium conversion coatings on AZ31 magnesium alloys. J Electrochem Soc 152(2):B54–B59

Luo SL et al (2006) New anodizing process for magnesium alloys. J Cent South Univ Technol 13(2):141–145

Massad SK, Basaly MA, Agudelo LF (1995) Process and composition for sealing anodized aluminum surfaces. US 5,478,415

Mogoda AS (1999) Influence of some parameters on passivation of zirconium and the stability of the anodic oxide film. Corrosion 55(9):877–882

Ono S et al (1998) Oxide films formed on magnesium and magnesium alloys by anodizing and chemical conversion coating. Corrosion Rev 16(1–2):175–190

Ono S, Asami K, Masuko N (2001) Mechanism of chemical conversion coating film growth on magnesium and magnesium alloys. Mater Trans 42(7):1225–1231

Quach NC, Uggowitzer PJ, Schmutz P (2008) Corrosion behaviour of an Mg-Y-RE alloy used in biomedical applications studied by electrochemical techniques. C R Chim 11(9):1043–1054

Ross PN, Henshaw GS, MacCulloch JA (1998) Anodising magnesium and magnesium alloys. WO 984289

Rupp VL, Surprenant K (2005) Solvent cold cleaning and vapor degreasing. In: ASM handbook

Schmeling EL, Roschenbleck B, Weidemann MH (1990) Method of producing protective coatings that are resistant to corrosion and wear on magnesium and magnesium alloys. US Patent 4,978,432

Simaranov AY, Marshakov AI, Mikhailovskii YN (1989) Formation of conversion coatings on magnesium in moderately acid chromate solutions. Prot Metal 25(5):611–618

Simaranov AY, Marshakov AI, Mikhailovskii YN (1992) The composition and protective properties of chromate conversion coatings on magnesium. Prot Metal 28(5):576–580

Takai M, Takaya M (2008) Influence of conversion coating on magnesium and aluminum alloys by adhesion method. Mater Trans 49(5):1065–1070

Tomlinson CE (1988) Chromate-free conversion coatings for metals. US Patent 5,759,244

Tomlinson CE (1995) Conversion coatings for metal surfaces. US Patent 5,380,374

Tomlinson CE (1999) Conversion coatings for metals using group IV-A metals in the presence of little or no fluoride and little or no chromium. US Patent 5,952,049

Umehara H, Takaya M, Kojima Y (2001) An investigation of the structure and corrosion resistance of permanganate conversion coatings on AZ91D magnesium alloy. Mater Trans 42(8):1691–1699

Umehara H, Takaya M, Terauchi S (2003) Permanganate conversion coatings for magnesium alloys. Magnes Alloy 419–4((Pts 1 and 2)):883–888

Wang C et al (2009) Cerium conversion coatings for AZ91D magnesium alloy in ethanol solution and its corrosion resistance. Corros Sci 51(12):2916–2923

Weng WP et al (2006) Influence of pH value on chromate-free conversion coating for magnesium alloys. Trans Nonfer Metals Soc China 16:S1819–S1822

Wojtala A (2011) Properties of polyethylene filled with magnesium hydroxide modified with a silane compound and promoted with iron(Iii) acetylacetonate. Polimery 56(2):114–120

Wu SS et al (2005) Properties of conversion coating of magnesium alloys by a phosphatepermanganate solution. Magnes Sci Technol Appl 488–489:665–668

Wu CS et al (2007) Study on the anodizing of AZ31 magnesium alloys in alkaline borate solutions. Appl Surf Sci 253(8):3893–3898

Xue DC et al (2011) Corrosion protection of biodegradable magnesium implants using anodization. Mater Sci Eng C Mater Biol Appl 31(2):215–223

Yong Z et al (2008) Molybdate/phosphate composite conversion coating on magnesium alloy surface for corrosion protection. Appl Surf Sci 255(5):1672–1680