The corrosion behavior of sputter-deposited amorphous copper-tantalum alloys in 12 M HCl

Characterization of Surface of Amorphous Ni-Nb-Ta-P Alloys Passivated in a 12 kmol/m<SUP>3</SUP> HCl Solution

“…They become higher than that of tantalum and are located in the passive region of tantalum, similarly to the other tantalum containing alloys. 3,16) Accordingly, the alloys containing 15 at% or more tantalum are passivated spontaneously in agreement with high corrosion resistance in the aggressive concentrated hydrochloric acid. 8) In contrast to these alloys, the open circuit potentials for the alloys with 10 at% or less tantalum decrease rapidly down to about À0:19 V within 3.6 ks and stay at low potentials from À0:18 to À0:21 V depending on alloy tantalum content and are located in the active region of the alloys.…”

“…11,12) The composition and thickness of surface film and the composition of the substrate alloy immediately under the surface film were quantitatively determined by a previously proposed method, 13) in which the original method 12,14) was modified more conveniently. The 16) 2.98, 17) and 0.79, 18) where superscripts m and ox denote the metallic and oxidized states of elements, respectively. The open circuit potentials of the alloys containing 15 at% or more tantalum are also about À0:12 V just after immersion increase rapidly within 3.6 ks immersion and further increase gradually with immersion time and with alloy tantalum content.…”

“…Similar trend has been observed for high tantalum-bearing alloys in strong acid solution. 16,22) In contrast to high tantalum-bearing alloys, a stable passive film cannot be formed for the low tantalum-bearing alloys. Figures 8(a) and (b) shows the change in the cationic fraction in the surface film and the atomic fraction in the underlying alloy surface, respectively, for the amorphous 5Ta alloy as a function of immersion time.…”

A non–destructive compositional analysis of thin surface films formed on W–xTa alloys by angle resolved X–ray photoelectron spectroscopy

“…For angle-resolved XPS, the angle between the alloy specimen surface and the direction of photoelectron to the detector (take-off angle of photoelectrons) was changed by using tilted-specimen holders at 30°, 45°, 60° and 90° as discussed elsewhere [55]. The photo-ionization cross-section of the W 4f and T a 4f electrons relative to the O 1s electrons used were 2.97 [58] and 2.617 [59], respectively.…”

High Corrosion Resistant Ni-Based Glassy Alloys in Boiling Nitric Acid Solutions

“…(3) The 20 at% Nb content in alloy could provide a strong passivating ability. Furthermore, due to higher corrosion resistance of Ta element than that of Nb element, 14,15) the addition of Ta to the Ni-Nb-Zr glassy alloy is expected to improve the corrosion resistance in such severe environments. So, the present work aims to investigate the corrosion behavior of the Ni-Nb-Zr-Ta glassy alloys in boiling HNO 3 solutions.…”