Composition and Performance of Nanostructured Zirconium Titanium Conversion Coating on Aluminum‐Magnesium Alloys

Abstract

Nanostructured conversion coating of Al-Mg alloy was obtained via the surface treatment with zirconium titanium salt solution at 25°C for 10 min. The zirconium titanium salt solution is composed of tannic acid 1.00 g·L−1, K2ZrF60.75 g·L−1, NaF 1.25 g·L−1, MgSO41.0 g/L, and tetra-n-butyl titanate (TBT) 0.08 g·L−1. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrum (FT-IR) were used to characterize the composition and structure of the obtained conversion coating. The morphology of the conversion coating was obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results exhibit that the zirconium titanium salt conversion coating of Al-Mg alloy contains Ti, Zr, Al, F, O, Mg, C, Na, and so on. The conversion coating with nm level thickness is smooth, uniform, and compact. Corrosion resistance of conversion coating was evaluated in the 3.5 wt.% NaCl electrolyte through polarization curves and electrochemical impedance spectrum (EIS). Self-corrosion current density on the nanostructured conversion coating of Al-Mg alloy is9.7×10-8A·cm-2, which is only 2% of that on the untreated aluminum-magnesium alloy. This result indicates that the corrosion resistance of the conversion coating is improved markedly after chemical conversion treatment.

Corrosion Behavior of a Conversion Coating Based on Zirconium and Colorants on Galvanized Steel by Electrodeposition

“…This means that the same fundamental phenomenon may have occurred in all these coatings, but along a different effective area in each case. The appearance of these semicircles in the Bode diagrams of the coated samples showed that the corrosion process involves these coatings more than a time constant; this indicates that a double layer in the coating/electrolyte interface exists [3,7,8]. As it is known, each reaction or physical phenomenon presents one time constant [7].…”

“…Therefore, a post treatment is necessary to prevent the previous white corrosion. Well-known coatings based in chromium (VI) have been used for a long time and now they are being prohibited because of their toxicity [3][4][5]. The trivalent chrome coating came up as an environmentally friendly solution but this coat does not confer the yellow color like the hexavalent chrome coating does [6].…”

Preparation of Ti–Zr-Based Conversion Coating on 5052 Aluminum Alloy, and Its Corrosion Resistance and Antifouling Performance

“…As shown in Figure 3a, the absorption around 3433 cm −1 is assigned to the absorptions of a hydroxyl group. The characteristic peaks at the range of 2839-2978 cm −1 are assigned to the absorptions of C-H [16,22]. The characteristic peak at around 1631 cm −1 is assigned to the absorptions of Al-O.…”

Surface Pretreatments of AA5083 Aluminum Alloy with Enhanced Corrosion Protection for Cerium-Based Conversion Coatings Application: Combined Experimental and Computational Analysis

“…Although chromate conversion coatings (CrCCs) have been extensively used to achieve high corrosion resistance [3], Cr is toxic and carcinogenic [4]. Thus, a variety of environmentally friendly conversion coatings have been developed, such as phosphate conversion coatings [5], molybdate conversion coatings [6], zirconium/titanium conversion coatings [7,8], and cerium conversion coatings (CeCCs) [9,10]. These coatings can improve Al alloys' corrosion resistance and adhesion properties, making them promising alternatives to Cr conversion coating [11].…”