Abstract：The silicate conversion coating was prepared by immersing hot dip galvanized (HDG) steel in sodium silicate solution with a SiO2∶Na2O molar ratio of 1.00 or 3.50, respectively. The corrosion resistance of coatings was investigated by neutral salt spray (NSS) test, Tafel polarization and electrochemical impedance spectroscopy (EIS) measurement. NSS corrosion process of the coatings scratched by the edge of knife was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the superior corrosion resistance and self healing ability are obtained from the silicate coating pretreated in sodium silicate solution with higher SiO2∶Na2O molar ratio. During the corrosion process, silicate anions migrate from the coating to the scratch, on which a new passive coating composed of Zn, O and Si is formed and the corrosion is suppressed. Moreover, it is observed that by the atomic force microscopy (AFM), the silicate coatings obtained in the sodium silicate solution with molar ratio of 3.50 is more compact, which is favor of the migration of silicate anions. The detail of corrosion process of the scratches on silicate coatings is discussed.
袁美蓉, 卢锦堂, 孔纲, 车淳山. 热镀锌层上硅酸盐膜的耐蚀性和自愈性[J]. 材料工程, 2012, 0(6): 48-53.
YUAN Mei-rong, LU Jin-tang, KONG Gang, CHE Chun-shan. Corrosion Resistance and Self Healing Ability of Silicate Conversion Coatings on Hot Dip Galvanized Steels. Journal of Materials Engineering, 2012, 0(6): 48-53.
参考文献［1］卢锦堂，孔 纲，陈锦红，等. 热浸镀锌性能及质量要求［J］. 材料保护, 2000, 33(3): 21-23.［2］CHEN Jiann-ruey, CHAO Huei-yun, LIN Yuh-lin, et al. Studies on carbon steel corrosion in molybdate and silicate solutions as corrosion inhibitors ［J］. Surface Science, 1991, 247(2-3): 352-359. ［3］ARAMAKI K. The inhibition effects of chromate-free, anion inhibitors on corrosion of zinc in aerated 0.5 M NaCl ［J］. Corrosion Science, 2001, 43(3): 591-604.［4］HAHN J J, MCGOWAN N G, HEIMANN R L, et al. Modification and characterization of mineralization surface for corrosion protection ［J］. Surface & Coatings Technology, 1998, 108-109(1-3): 403-407.［5］VEERARAGHAVAN B, SLAVKOV D, PRABHU S, et al. Synthesis and characterization of a novel non-chrome electrolytic surface treatment process to protect zinc coatings ［J］. Surface & Coatings Technology, 2003, 167(1): 41-51.［6］VEERARAGHAVAN B, HARAN B, SLAVKOV D, et al. Development of a novel electrochemical method to deposit high corrosion resistant silicate layers on metal substrates ［J］. Electrochemical and Solid-State Letters, 2003, 6(2): B4-B8.［7］KUMARAGURU S P, VEERARAGHAVAN B, POPOV B N. Development of an electroless method to deposit corrosion-resistant silicate layers on metallic substrates ［J］. Journal of the Electrochemical Society, 2006, 153(7): B253-B259.［8］DIKINIS V, NIAURA G, REZAITE V, et al. Formation of conversion silicate films on Zn and their properties ［J］. Transactions of the Institution of Metal Finishing, 2007, 85(2): 87-93.［9］SUDA A, ASARI M. Behavior and mechanism of corrosion protection for galvanized steels by self-healing effect of chromate coatings ［J］. Zairyo to Kankyo/ Corrosion Engineering, 1997, 46(2): 95-102.［10］RAMSEY J D, McCREERY R L. In situ Raman microscopy of chromate effects on corrosion pits in aluminum alloy ［J］. Journal of the Electrochemical Society, 1999, 146(11): 4076-4081.［11］KENDIG M, JEANJAQUET S, ADDISION R, et al. Role of hexavalent chromium in the inhibition of corrosion of aluminum alloys ［J］. Surface & Coatings Technology, 2001, 140(1): 58-66.［12］XU Yu-ye, LIN Bi-lan. Effect of silicate pretreatment, post-sealing and additives on corrosion resistance of phosphated galvanized steel ［J］. Transactions of Nonferrous Metals Society of China, 2007, 17(6): 1248-1253.［13］LIN Bi-lan, LU Jing-tang, KONG Gang. Synergistic corrosion protection for galvanized steel by phosphating and sodium silicate post-sealing ［J］. Surface & Coatings Technology, 2008, 202(9): 1831-1838.［14］ARAMAKI K. Self-healing mechanism of an organosiloxane polymer film containing sodium silicate and cerium(III) nitrate for corrosion of scratched zinc surface in 0.5 M NaCl ［J］. Corrosion Science, 2002, 44 (7): 1621-1632.［15］ARAMAKI K. Preparation of chromate-free, self-healing polymer films containing sodium silicate on zinc pretreated in a cerium (III) nitrate solution for preventing zinc corrosion at scratches in 0.5 M NaCl ［J］. Corrosion Science, 2002, 44 (6): 1375-1389.（下转第79页）材料工程