Effect of cerium nitrate and salicylic acid on the titanium–zirconium chemical conversion coating of 6061 aluminum alloy. Issue 2 (29th January 2020)

• Record Type: Journal Article
• Authors: Wang, Xiaobo; Zhan, Wen; Gui, Boyi
• Is Part Of: Anti-corrosion methods and materials. Volume 67:Issue 2(2020)
• Page Start: 205
• Page End: 213
• Publication Date: 2020-01-29
• Subjects: Corrosion resistance -- Aluminum alloy -- Conversion coating -- Cerium nitrate -- Salicylic acid; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1108/ACMM-10-2019-2201
• Languages: English
• ISSNs: 0003-5599

Abstract

Abstract : Purpose: The purpose of this paper is to develop a chrome-free and phosphorus-free chemical conversion coating with good corrosion resistance, a novel chemical conversion coating was prepared by adding cerium nitrate hexahydrate and salicylic acid in the treatment solution containing titanium/zirconium ions on 6061 aluminum alloy. Design/methodology/approach: Compared with the AA6061 aluminum alloy matrix, the self-corrosion potential of the conversion coating is significantly positively shifted, the self-corrosion current density is greatly reduced and its corrosion resistance is significantly improved. Morphology and composition of the conversion coatings were observed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microdomain structure of conversion coatings at different formation stages was analyzed by electron probe microanalyzer. Findings: An optimized preparation technique of titanium–zirconium chemical conversion coating for AA6061 aluminum alloy is obtained: H2 TiF6 4 mL/L, H2 ZrF6 0.4 mL/L, salicylic acid 0.35 g/L, Ce(NO3 )3 ·6H2 O 0.14 g/L, reaction temperature 30°C, reaction time 120 s and pH 4.0. Originality/value: The coating forms on the Al(Fe)Si intermetallic compound, and Ce 3+ is preferentially adsorbed on the intermetallic compound. The hydrolysis of Ce 3+ causes the local pH of the solution to decrease, which promotes matrix dissolution and charge migration. As the microanode/microcathode reaction occurs, the local pH of the solution increases, and Al2 O3 /ZrO2 /TiO2 begins to deposit on the surface of the metal substrate.