Characteristics of Colored Passive Layers on Zirconium: Morphology, Optical Properties, and Corrosion Resistance

Abstract

Brightly colored and uniform passive layers on Zr can be formed by applying alternating current (ac) voltage (V(ac)) for 10 s in 10 wt % aqueous Na(2)SO(4) solution at T = 298 K. The coloration originating from iridescence can be fine-tuned by adjusting V(ac) in the 10-80 V range. Visible light microscopy analysis shows that different grains reveal two or three different colors due to the polycrystalline nature of Zr, and the resultant coloration is the sum of these contributions. Reflectance spectroscopy spectra show maxima that can be related to the coloration displayed by various grains. Surface morphology and roughness in the micrometer and nanometer ranges are examined using stylus surface profilometry and atomic force microscopy. The formation of colored passive layers on polished Zr makes them smoother but their formation on etched Zr decreases the roughness in the case of low V(ac) and increases in the case of high V(ac). Focused ion beam and scanning electron microscopy are used to determine the thickness (d) of the colored passive layer on etched Zr. It is found that d is in the 51-264 nm range and increases linearly with V(ac). Scanning transmission electron microscopy and electron back scattered diffraction measurements demonstrate that the colored passive layers are uniform and crystalline in nature. Corrosion behavior of the colored passive layers in 1 wt % aqueous NaCl solution is examined using inductively coupled plasma-mass spectrometry. The results indicate that the polished samples hardly undergo any corrosion and the amount of dissolved Zr does not exceed 12 ppb even after exposure for 56 days. On the other hand, the corrosion of the etched samples is ~3 orders of magnitude greater than that of the polished ones, and the amount of dissolved Zr approaches 970 ppb after exposure for 56 days. Corrosion behavior of etched and colored passive layers on Zr in 1 wt % aqueous NaCl solution is also analyzed by recording potentiodynamic polarization curves in the -1.0 to 3.0 V vs RHE range at a scan rate of s = 1 mV s(-1) and at T = 298 K. They have similar shapes but the formation of colored passive layers decreases the current density (j) at any given potential (E), and the thicker the passive layer the greater the reduction in j. The development of colored passive layers on etched Zr increases the corrosion potential (E(corr)) and decreases the corrosion current density (j(corr)).

Characteristics of Colored Passive Layers on Titanium: Morphology, Optical Properties, and Corrosion Resistance

“…Wire electrodes were then treated in the etching solution described above, rinsed with UHP water, and sonicated in an ultrasonic bath (Branson) for 1 min. All Ti electrodes were immersed in a single compartment electrochemical cell where the electrochemical coloration was carried out by application of AC voltage ( V AC ). , A counter electrode of Pt foil spot-welded to a Pt wire (Johnson-Matthey, 99.9 wt %) was employed; with a real surface area of a minimum 10 times greater than that of the Ti electrode. The distance between the working (Ti) and counter (Pt) electrodes was maintained at ca.…”

“…We previously published an extensive study on the electrochemical passivation of Zr and the resulting properties achieved . Although Ti and Zr possess many similar properties, they still reveal certain differences, such as grain structure and size, that are of particular relevance to this research.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…Results from SEM-EDXRF showed that stellite 6 particles penetrate into the copper plates and mechanical tests indicated that this process increased hardness of the material. Holmberg et al 37 characterized the brightly coloured uniform passive layers formed on zirconium by electrochemical treatments using many different methods. Prolometry and AFS were used to examine the surface roughness and surface morphology.…”

Existence of Resistive Switching Memory and Negative Differential Resistance State in Self-Colored MoS2/ZnO Heterojunction Devices

“…Self-colored films can be grown on many metal substrates such as titanium, steel, niobium, tantalum, and zirconium. 5 Recently, there have been many methods used in coloring various metals such as electrochemical techniques 6,7 and magnetic sputtering methods, 8,9 etc. However, the magnetron sputtering technique is a dominant method of syntheses of thin films which is extensively used at laboratory or industrial scales for the preparation of various types of single or multioxides or other oxide-based composite layers.…”