Stainless steel 304 coated with aluminum using Hot-Dipping Alumina (HDA) method after pre-plated with Nickel to prevent mutual diffusion of iron and aluminum was investigated; and then Micro-Arc Oxidation (MAO) was performed using aluminate solution to improve the surface properties of steel.
Nickel Electroplating successfully buffered diffusion of iron atoms into the aluminum layer, preventing interfaces of materials from formation of brittle structure such as FeAl3 and Fe2Al5. During the Hot-Dipping Aluminum process, nickel reacts with aluminum to form interphases (NiAl3, Ni2Al5 and Ni3Al) which exhibit good hardness and good wear resistance.
Aluminum shows a constant reaction rate with nickel, making similar or even the same interphase layer thickness (~2μm for NiAl3 (interphase 1), ~1μm for Ni2Al5 (interphase 2) and 1μm for Ni3Al (interphase 3)) for a constant dipping-time. The reaction between Al and Ni layers begun with formation of interphase 1 and then continued by interphase 2 and for the last layer interphase 3. Along with increasing of dipping-time, nickel will scatter to all over the coating and take reaction with aluminum in form of dot-like or beam-like. For dipping-time more than 60 seconds, nickel coating of 54-60μm will disappear, leading to contact and reaction between aluminum and iron, forming Fe-Al phase. Therefore, dipping time less than 60 seconds will be the best choice for the dipping-time variable.
At last, MAO is successfully applied for Stainless Steel 304 material after being plated by nickel and dipped into the molten alumina respectively, producing aluminum oxide on the surface which enhances the surface properties of stainless steel such as hardness and corrosion resistance.
Fundamental data of MAO results in Aluminate solution and Silicate solution for Aluminum 6061 is also investigated and compared. The results shows better performance of hardness for Al2O3 in aluminate solution than those in Silicate solution. The maximum hardness of aluminate-solution is 2400HV, while that of MAO specimen using silicate solution is 1600HV.
The other comparisons of parameters such as voltage, time, etc., were investigated and discussed as well.

Stainless steel 304 coated with aluminum using Hot-Dipping Alumina (HDA) method after pre-plated with Nickel to prevent mutual diffusion of iron and aluminum was investigated; and then Micro-Arc Oxidation (MAO) was performed using aluminate solution to improve the surface properties of steel.
Nickel Electroplating successfully buffered diffusion of iron atoms into the aluminum layer, preventing interfaces of materials from formation of brittle structure such as FeAl3 and Fe2Al5. During the Hot-Dipping Aluminum process, nickel reacts with aluminum to form interphases (NiAl3, Ni2Al5 and Ni3Al) which exhibit good hardness and good wear resistance.
Aluminum shows a constant reaction rate with nickel, making similar or even the same interphase layer thickness (~2μm for NiAl3 (interphase 1), ~1μm for Ni2Al5 (interphase 2) and 1μm for Ni3Al (interphase 3)) for a constant dipping-time. The reaction between Al and Ni layers begun with formation of interphase 1 and then continued by interphase 2 and for the last layer interphase 3. Along with increasing of dipping-time, nickel will scatter to all over the coating and take reaction with aluminum in form of dot-like or beam-like. For dipping-time more than 60 seconds, nickel coating of 54-60μm will disappear, leading to contact and reaction between aluminum and iron, forming Fe-Al phase. Therefore, dipping time less than 60 seconds will be the best choice for the dipping-time variable.
At last, MAO is successfully applied for Stainless Steel 304 material after being plated by nickel and dipped into the molten alumina respectively, producing aluminum oxide on the surface which enhances the surface properties of stainless steel such as hardness and corrosion resistance.
Fundamental data of MAO results in Aluminate solution and Silicate solution for Aluminum 6061 is also investigated and compared. The results shows better performance of hardness for Al2O3 in aluminate solution than those in Silicate solution. The maximum hardness of aluminate-solution is 2400HV, while that of MAO specimen using silicate solution is 1600HV.
The other comparisons of parameters such as voltage, time, etc., were investigated and discussed as well.

1. Dunleavy, C.S., et al., Characterisation of discharge events during plasma electrolytic oxidation. Surface & Coatings Technology, 2009. 203: p. 3410-3419.
2. Matykina, E., et al., Real-time imaging of coating growth during plasma electrolytic oxidation of titanium. Electrochimica Acta, 2007. 53: p. 1987-1994.
3. Wang, C., D. Zhang, and Y. Jiang, Growth process and wear resistance for ceramic coatings formed on Al–Cu–Mg alloy by micro-arc oxidation. Applied Surface Science, 2006. 253: p. 674-678.
4. Yao-hui, L. and L. Song, Current Status and Progress of Study on Micro-Arc Oxidation Technology. Materials Protection, 2005. 38: p. 36-39.
5. Yerokhin, A.L., et al., Spatial characteristics of discharge phenomena in plasma electrolytic oxidation of aluminium alloy. Surface and Coatings Technology 2004. 177 –178: p. 779–783.
6. Pokhmurskii, V., et al., Plasma Electrolytic Oxidation of Arc-Sprayed Aluminum Coatings. Journal of Thermal Spray Technology, 2007. 16: p. 998-1004.
7. Wei, T., F. Yan, and J. Tian, Characterization and wear- and corrosion-resistance of microarc oxidation ceramic coatings on aluminum alloy. Journal of Alloys and Compounds, 2004. 389: p. 169-176.
8. Gu, W., et al., Deposition of duplex Al2O3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation. Applied Surface Science, 2006. 252: p. 2927–2932.
9. Wu, Z., et al., Structure and mechanical properties of ceramic coatings fabricated by plasma electrolytic oxidation on aluminized steel. Applied Surface Science, 2007. 253: p. 8398–8403.
10. KRIT, P.B.L., Microarc Discharge Oxidizing (MDO). 2012.
11. KRIT, P.B.L., Microarc Discharge Oxidizing (MDO) 2012.
12. Tseng, C.-C., et al., The influence of sodium tungstate concentration and anodizing conditions on microarc oxidation (MAO) coatings for aluminum alloy. Surface & Coatings Technology, 2012. 206: p. 3437–3443.
13. Zhenga, H.Y., et al., The effects of Na2WO4 concentration on the properties of microarc oxidation coatings on aluminum alloy. Materials Letters, 2005. 59: p. 139–142.
14. H.X.Li, et al., CharacterizationofAl2O3ceramiccoatingson6063aluminumalloy preparedinborateelectrolytesbymicro-arcoxidation. Journal of Alloys and Compounds, 2008. 462: p. 99–102
15. Tanga, M., et al., Preparation Al2O3/ZrO2 composite coating in an alkaline phosphate electrolyte containing K2ZrF6 on aluminum alloy by microarc oxidation. Applied Surface Science, 2012. 258: p. 5869– 5875.
16. Li Wang, L.C., et al., The influence of additives on the stability behavior of electrolyte, discharges and PEO films characteristics. Journal of Alloys and Compounds 2010. 493: p. 445–452.
17. Rudnev, V.S., et al., Anodic spark deposition of P, Me(II) or Me(III) containing coatings on aluminium and titanium alloys in electrolytes with polyphosphate complexes. Journal of Electroanalytical Chemistry, 2001. 497: p. 150–158.
18. Matykina, E., et al., Incorporation of zirconia into coatings formed by DC plasma electrolytic oxidation of aluminium in nanoparticle suspensions. Applied Surface Science, 2008. 255: p. 2830–2839.
19. Liang, J., L. Hua, and J. Haoa, Preparation and characterization of oxide films containing crystalline TiO2 on magnesium alloy by plasma electrolytic oxidation. Electrochimica Acta, 2007. 52: p. 4836–4840.
20. Yerokhin, A.L., V.V. Lyubimov, and R.V. Ashitkov, Phase During Formation in Ceramic Coatings Plasma Electrolytic Oxidation of Aluminium Alloys. Ceramic International, 1998. 24: p. 1-6.
21. Zhitomirskya, V.N., et al., X-ray photoelectron spectroscopy of nano-multilayered Zr–O/Al–O coatings deposited by cathodic vacuum arc plasma. Applied Surface Science 2010. 256: p. 6246–6253.
22. Matykina∗, E., et al., Investigation of the growth processes of coatings formed by AC plasma electrolytic oxidation of aluminium. Electrochimica Acta, 2009. 54: p. 6767–6778.
23. Wu, H., et al., Ultra-hard ceramic coatings fabricated through microarc oxidation on aluminium alloy. Applied Surface Science 2005. 252: p. 1545–1552.
24. Guanglianga, Y., et al., T he effects of current density on the phase composition and microstructure properties of micro-arc oxidation coating. Journal of Alloys and Compounds 2002. 345: p. 196–200.
25. Wanga, Y., et al., Dependence of growth features of microarc oxidation coatings of titanium alloy on control modes of alternate pulse. Materials Letters, 2004. 58: p. 1907– 1911.
26. Tanga, H., et al., Influence of FeSO4 concentration on thermal emissivity of coatings formed on titanium alloy by micro-arc oxidation. Applied Surface Science, 2011. 257: p. 10839– 10844.
27. Li, L.-H., et al., Biocompatibility of titanium implants modified by microarc oxidation and hydroxyapatite coating. Wiley InterScience, 2005.
28. Sulzer, An introduction to Thermal Spray. 2012.
29. Cheng, W.-J. and C.-J. Wang, Study of microstructure and phase evolution of hot-dipped aluminide mild steel during high-temperature diffusion using electron backscatter diffraction. Applied Surface Science, 2011. 257: p. 4663–4668.
30. Cheng, W.-J. and C.-J. Wang, EBSD study of crystallographic identification of Fe–Al–Si intermetallic phases in Al–Si coating on Cr–Mo steel. Applied Surface Science 2011. 257: p. 4637–4642.
31. Cheng, W.-J. and C.-J. Wang, Observation of high-temperature phase transformation in the Si-modified aluminide coating on mild steel using EBSD. M A T E R I A L S C H A R A C T E R I Z A T I O N, 2 0 1 0. 6 1: p. 4 6 7 – 4 7 3.
32. Cheng, W.-J. and C.-J. Wang, Growth of intermetallic layer in the aluminide mild steel during hot-dipping. Surface & Coatings Technology, 2009. 204: p. 824–828.
33. Changa, Y.-Y., W.-J. Cheng, and C.-J. Wang, M A T E R I A L S C H A R A C T E R I Z A T I O N, 2 0 0 9. 6 0 p. 1 4 4– 1 4 9

34. Kobayashi, S. and T. Yakou, Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment. Materials Science and Engineering, 2002. A338: p. 44-53.
35. Cheng, W.-J. and C.-J. Wang, Characterization of intermetallic layer formation in aluminide/nickel duplex coating on mild steel. M A T E R I A L S C H A R A C T E R I Z A T I O N 2 0 1 2 6 9: p. 6 3 – 7 0.
36. Dan, B., C. Georgeta, and A. Angel, Critical Analysis of Al-Ni Phase Diagrams. Metalurgia International, 2006. 11: p. 36 - 45.
37. ROHATGI, P.K. and B.C. PAI, EFFECT OF MICROSTRUCTURE AND MECHANICAL PROPERTIES ON THE SEIZURE RESISTANCE OF CAST ALUMINIUM ALLOYS. Wear,, 1974. 28 p. 353-367.
38. Bari, G.D., Nickel Plating, in ASM Handbook, Surface Engineering. 1994, ASM International, Materials Park: OH. p. 201.
39. Postigo, M.V., New methods for the analytical control of a nickel electroplating bath. Application of chemometric techniques. 2010, Universidad del Pais Vasco. p. 98.