Electrochemical Behavior of Zinc Layers Passivated in Phosphate Solutions
Abstract
Phosphate conversion coatings are used on the galvanized steel. By forming a thin protective film on the surface of the steels this treatment enhances corrosion resistance. This paper presents studies on phosphate passivation solutions. The results of treatments for different treatment times and more compositions were analyzed in terms of layer thickness, structural aspects, adherence, and continuity of films. Corrosion resistance was assessed by the linear voltammetry test. Activepassive curves were analysed and compared with unpassivated galvanised samples. For each passivation solution experimented Tafel curves were drawn and corrosion rates were determined. The optimal passivation conditions were settled as function on obtained results.
References
[2]. Duprat, J.J. - CrVI Free Conversion Coatings on Zinc and Zinc Alloy Coatings, CONVENTYA SAS, November, (2007).
[3]. LIU Guangming, YU Fei, YANG Liu, TIAN Jihong, DU Nan - Cerium-tannic acid passivation treatment on galvanized steel, RARE METALS, Vol. 28, No. 3, Jun, (2009), p. 284.
[4]. Bexell U. and Grehk T.M. - A corrosion study of hot-dip galvanized steel sheet pre-treated with γ-mercaptopropyltrimethoxysilane, Surf. Coat. Technol., (2007), 201 4734.
[5]. Deflorian F., Rossi S., Fedrizzi L., and Bonora P.L. - EIS study of organic coating on zinc surface pretreated with environmentally friendly products, Prog. Org. Coat., (2005), 52:271.
[6]. Swaminatha P. Kumaraguru, Basker Veeraraghavan, and Branko N. Popov - Development of an Electroless Method to Deposit Corrosion-Resistant Silicate Layers on Metallic Substrates, Journal of The Electrochemical Society, 153 _7_ B253-B259 _2006.
[7]. Danqing Zhu, Wim J. van Ooij - Enhanced corrosion resistance of AA 2024-T3 and hot-dip galvanized steel using a mixture of bis-[triethoxysilylpropyl]tetrasulfide and bis-[trimethoxysilylpropyl]amine, Electrochimica Acta 49 (2004) 1113–1125.
[8]. Lorin G. - Phosphating of metals: constitution, physical chemistry and technical applications of phosphating solutions [M]. Hampton Hill: Finishing Publications, (1974), 146−155.
[9]. Freeman D B. - Phosphating and metal pre-treatment [M]. New York: Industrial Press, (1986), 134−139.
[10]. Rausch W. - The phosphating of metals [M]. Ohio: ASM International, (1990), 112−116.1−3.
[11]. Ross, W.A. - British Patent 3,119 (1869).
[12]. Sankara Narayanan, T.S.N. - Surface Pretreatment by Phosphate Conversion Coatings. A Review, Rev.Adv.Mater.Sci. 9 (2005) 130-177.
[13]. Song, Y.K., Mansfeld, F. - Development of a Molybdate–Phosphate–Silane–Silicate (MPSS) coating process for electrogalvanized steel, Corrosion Science 48 (2006) 154–164.
[14]. Tang, P.T., Nielsen, G.B., Moeller, P. - Plat. Surf. Finish. 81 (1994) 11.
[15]. ***, ASM Metals Handbook vol. 13, Corrosion, (1992) 67-71.
