Deformation of Anodic Oxide Films

Abstract

Tantalum oxide films on smooth, pure substrates can be deformed as much as 50% before fracture. On surfaces containing impurity particles the films contain many flaws which nucleate cracks after relatively little deformation. Zirconium oxide films showed some evidence of deformation, but much less than tantalum oxide. Aluminum oxide films showed no evidence of deformation.Protection against corrosion is usually afforded by a thin film of reaction product. The behavior of such a film during deformation of the underlying metal would be of great importance in determining corrosion under such conditions and may play a decisive role in stress corrosion cracking and corrosion fatigue. It is usually assumed that reaction films are brittle, and one currently popular theory of stress corrosion cracking asserts that repeated cracking of the passive film allows continued corrosion. Bradhurst and Leach (1) have shown that barrier-type anodic oxide films on aluminum are brittle, while Edeleanu and Law (2) have demonstrated that both porous anodic aluminum oxide films and the natural corrosion film on aluminum are brittle. Young (3), on the other hand, reported that anodic films on tantalum changed color during deformation of the metal indicating some deformation of the oxide, and Dunn (4) has told us that anodic films on tantalum deform along with the substrate when tantalum sheet is rolled. In this paper we report the use of a new technique to obtain quantitative information about the deformation of anodic films on aluminum, zirconium, and tantalum.

Reassessment of degradation mechanisms in anodic tantalum oxide capacitors under high electric fields

“…1a, b) after exposure to the same conditions. This strongly suggests that cracks are more easily formed on rough ATO/Ta systems exposed to high electric fields [23,24].…”

Growth and Electrochemical Stability of Compact Tantalum Oxides Obtained in Different Electrolytes for Biomedical Applications

“…Eliezer & Brandon 24 apud Bubar & Vermilyea 25 observed plastic deformation around 50% for galvanostatic anodic films of Ta 2 O 5 obtained in acidic electrolytes, which indicates a highly adherent oxide for this feature in the proposed dimensions (thin film). In another research, Dunn 26 observed through lamination that tantalum samples with Ta 2 O 5 films grown galvanostatically in acidic electrolytes had high deformation capacity.…”

“…The analysis of microscopy with the topographic profile, allows to compare these results to studies already described in the literature 24,25 . Eliezer & Brandon 24 apud Bubar & Vermilyea 25 observed plastic deformation around 50% for galvanostatic anodic films of Ta 2 O 5 obtained in acidic electrolytes, which indicates a highly adherent oxide for this feature in the proposed dimensions (thin film).…”

Repassivation of 304 Stainless Steel Investigated with a Single Scratch Test

“…The deformation that occurred around the indenter damaged the passive film, for instance, by stretching, thinning, or cracking the film. 32 To simplify the model, the plastic deformation outside the scratch groove was ignored, since the deformation below the indenter was much larger than the deformation in the ridges. For the model, the charge density, q, to repair the damaged film was assumed to be a constant, q c , where q was calculated by Equations (2) and (3).…”