Microstructure characterisation of alumina coating on steel by PEO. (1st May 2013)

• Record Type: Journal Article
• Authors: Wang, Y L; Wang, M; Zhou, M; Li, B J; Amoako, G; Jiang, Z H
• Is Part Of: Surface engineering. Volume 29:Number 4(2013)
• Page Start: 271
• Page End: 275
• Publication Date: 2013-05-01
• Subjects: Alumina -- Coating -- Steel -- Corrosion -- PEO; Surfaces (Technology) -- Periodicals; Coatings -- Periodicals; 620.4405
• DOI: 10.1179/1743294412Y.0000000084
• Languages: English
• ISSNs: 0267-0844

Abstract

Abstract : Alumina ceramic coating was prepared on Q235 carbon steel by plasma electrolytic oxidation. The discharge process was analysed according to the voltage-time curve. The microstructure of the ceramic coating was investigated by scanning electron microscopy, X-ray diffractometry and energy dispersive X-ray spectroscopy. The bonding strength, thickness, hardness, surface roughness and corrosion properties of the coatings were studied. The results indicated that coating on Q235 carbon steel mainly consisted of  -Al2 O3 and γ -A12 O3 . The coating showed coarse and porous surface. The surface roughness of the coating was 1·8 μm, and the average diameter of the pores was 3-4 μm. The hardness of the coating was 1854 HV. The thickness of the coating was ∼28 μm, and the bonding strength was 23 MPa. The corrosion tests indicated that the corrosion current density of alumina coated Q235 in 3·5%NaCl was 8·289×10 −7 A cm −2, which was decreased by two orders of magnitude compared with the uncoated one. The corrosion potential was increased to −0·379 V, which shifted positively by 0·303 V compared to the uncoated one.