Alexis, Joël and Adrian, Denise
and Masri, Talal
and Petit, Jacques-Alain
Adherence of electrodeposited Zn-Ni coatings on EN AW2024 T3 aluminium alloy.
(2004)
Surface Engineering, 20 (2). 121-127. ISSN 0267-0844
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(Document in English)
PDF (Author's version) - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader 257kB |
Official URL: http://dx.doi.org/10.1179/026708404225010748
Abstract
The use of hexavalent chromium in surface treatments will be reduced in the future, as it is suspected to be carcinogenic. Electrodeposition of Zn-Ni, which is currently used on steel, represents a non-chromate alternative surface treatment for the corrosion protection of aluminium alloys. Zn-Ni coatings were electrodeposited onto an EN AW2024 T3 aluminium alloy sheet in a laboratory flow cell. To obtain several percentages of Ni in the coatings, solutions with different Ni2+ concentrations were used. The influence of a specific pretreatment to promote adherence, such as zincate immersion (109 g L-1 ZnO, 525 g L-1 NaOH) or phosphoric anodisation (36 wt-%H3PO4, 20°C) prior to electrodeposition was also investigated. The smoothness of the coating, measured on a three-dimensional roughness tester, increased when the percentage of Ni increased. This can be explained by a microstructural refinement observed using SEM and AFM. These microstructural changes are due to the evolution of the crystal structure of the coatings and can be observed by X-ray diffraction. The mechanical properties of the coatings (hardness and Young's modulus) were measured by microindentation and nanoindentation. The adherence of the coatings was tested by a scratch test and a three point bending test dedicated to coatings. The scratch behaviour of the coatings was a function of the percentage of Ni. The scratches observed indicate a ductile fracture for coatings with a low percentage of Ni and a brittle fracture for a high percentage of Ni. Bending tests demonstrated the favourable effect of pretreatments such as zincate immersion or phosphoric anodisation as well as adhesion enhancement as a function of increasing percentage of Ni.
Item Type: | Article |
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Additional Information: | Thanks to Maney Publishing editor. The definitive version is available at http://www.maneyonline.com/doi/abs/10.1179/026708404225010748 |
HAL Id: | hal-03601845 |
Audience (journal): | International peer-reviewed journal |
Uncontrolled Keywords: | |
Institution: | Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE) |
Laboratory name: | |
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Deposited On: | 07 Jan 2014 14:43 |
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