Studies on the sealing processes of corrosion resistant coatings formed on 2024 aluminium alloy with tartaric-sulfuric anodizing

• Published in: Surface & coatings technology Vol. 360; pp. 369 - 375
• Main Authors: Wang, Ruoxi, Wang, Lishi, He, Chunying, Lu, Min, Sun, Li
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.02.2019; Elsevier BV
• Subjects: Alloys; Aluminum base alloys; Anodizing; Corrosion resistance; Corrosion resistant alloys; Corrosion tests; Immersion tests (corrosion); Organic chemistry; Oxidation; Pitting (corrosion); Potassium permanganate; Product design; Protective coatings; Salt spray tests; Sealing; Sulfur; Tartaric-sulfuric acid anodizing (TSA); Corrosion resistance; Tartaric-sulfuric acid anodizing (TSA); Sealing
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2018.12.092

Anodizing and post-treatment of aluminium alloys can effectively improve their surface corrosion resistance. In this work, we demonstrate the effectiveness a potassium permanganate sealing (M-S) treatment of tartaric‑sulfuric anodized 2024 aluminium alloy. This post anodic oxidation process was performed by immersing samples in the electrolyte solution at 70 °C for 30 min. Immersion and salt spray tests show such a M-S sealing processing can result in much improved corrosion resistance. The M-S treated samples can resist 240 h of salt spray test without corrosion pitting. Detailed morphological, microstructural and chemical analyses have been used to reveal mechanistic effects of the M-S retreatment. Interfacial electrochemical impedance measurements were performed to directly compare the corrosion behaviors of Al alloys after different post-treatments. •Tartaric-sulfuric acid anodizing (TSA) for 2024 aluminium alloy and the post-treatment with potassium permanganate sealing can greatly improve its corrosion resistance to withstand 240 hours salt spray testing.•The impedance |Z| of the anodic coatings for TSA and four sealing processes show the increasing order: raw TSA coating, hot water, nickel salt, dichromate salt, and potassium permanganate sealing.