The Isolation of Surface Films from Copper

Abstract

A method for the isolation of oxide and sulfide films from copper has been developed. This depends on selective attack at the film-metal interface by a solution containing 3% ammonium acetate, and 0.25% bromine in dried methanol. When stripping was performed in contact with dry air, no film dissolution or contamination was detected.The isolation of surface films from metals frequently has permitted their detailed study by a variety of techniques such as transmission electron diffraction. In these cases the additional studies have assisted in clarifying the mechanism of surface reactions of metals.Satisfactory methods for isolating surface films currently are confined to relatively few metals (1). The iodine-anhydrous methanol method (2) has been used extensively for the isolation of oxide films from iron. This solution selectively attacks the filmmetal interface, thereby rapidly detaching the film. This technique has contributed materially to the understanding of the structure of passive films on iron (3)(4)(5). Similarly, the anhydrous bromine-methanol method is effective for stripping surface oxides from stainless steel (6). Both the bromine-methanol and iodine-methanol techniques have been used for the successful isolation of uncontaminated surface films from aluminum and some of its alloys (7, 8), However, these solutions do not preferentially attack the film-aluminum interface and so, unlike film stripping from ferrous materials, the whole of the metal must be dissolved.It has so far proved difficult to develop satisfactory film stripping techniques for copper and its alloys. Although thick surface films can be removed by amalgamation, invariably these are contaminated badly. Aqueous potassium cyanide solution also will isolate films from copper, but the films so removed undergo structural modification during stripping (13). The anodic film stripping method originally developed by Evans and Stockdale (9) has been used for the isolation of oxides from copper (10) and has been modified recently by Harris, et al. (11). Their method consisted of anodic treatment (5-10 v) in deaerated aqueous saturated potassium chloride solution. Contamination generally can be avoided by careful pH control, but on occasion residual particles of copper will remain attached to thin oxide films (12). This is a consequence of the need for complete retention of metallic contact during anodic stripping so that the last traces of metal can be removed. Accordingly, there is a definite need for an alternate simple film stripping method whereby surface films may be detached from copper by selective interracial corrosion in the absence of applied current. This paper describes the development of a suitable alternative film stripping method. Reflection and 417 transmission electron diffraction examinations were performed as part of this investigation to insure the absence of contamination and of any structural changes during stripping. Experimental and ResultsMaterials and specimen preparation.--All chemicals used in the investigation were o...

The Photogalvanic Disruption of Cuprous Oxide Films on Copper

“…Cupric oxide is dissolved by either method, and, therefore, the latter method can be considered an analysis for total oxidized copper, while the former method would result in an ambiguity if the oxide film contained an unknown amount of cupric oxide. The oxide film on copper treated at 300~ for about i0 rain has been shown to be essentially all cuprous oxide (13). Analysis of equal areas of an oxide film prepared under these conditions by both the dilute sulfuric acid and concentrated hydrochloric acid dissolution methods resulted in twice the concentration of copper in the hydrochloric acid solutions, thus verifying the self-consistency of the two methods.…”

“…Manuscript received Dec. 22, 1965; revised manuscript received April 29, 1966. This paper was presented at the Buffalo Meeting, Oct. [10][11][12][13][14] 1965.…”