THIN METAL FILMS AS CORROSION INDICATORS. Period covered: November 15, 1956 to November 15, 1957
In order to investigate the feasibility of using thin metal films deposited on glass or plastic substrates as integrating indicators of corrosive conditions, the corrosion rates of films of nine metals exposed to air atmospheres of controlled temperature and humidity have been studied. Of the metals iron, manganese, copper, nickel, cobalt, strontium, calcium, magnesium, and zinc, only films of iron and manganese proved worthy of more than a preliminary survey. A more intensive study of the corrosion properties and rates of iron and manganese films and of the bimetal pairs iron and copper and iron and gold was undertaken. This investigation disclosed the important role in metal film corrosion of the adsorbed gas layer normally present on glass substrates. This layer furnished the oxygen necessary for small particles of the oxides of iron to form at random sites in the film. These subsequently became elements of electrolytic cells in which the iron film acted as the anode in the presence of air at 25 C and 70 percent relative humidity. Destructive oxidation of the film thereafter proceeded by electrochemical processes. Rates of corrosion for iron films were controllable to a degree by removal of the adsorbed gas layer by pre-deposition heating of the substrate to 400 C or by more complete combination of the adsorbed layer with the metal of the film induced by post- deposition heating of the film. The former method reduced corrosion rates because of the removal of the oxygen supply for the formation of oxide ruclei, and the latter method increased the corrosion rate because of the greater number of oxide nuclei formed. Control of the corrosion rates of iron films under specific conditions of temperature and humidity appears feasible by control of the adsorbed gas layer and by introduction of cathodic particles either in the ferm of oxides or in the form of small volumes of a more electrically positive metal deposited at selected sites. (auth)
- Research Organization:
- Georgia Inst. of Tech., Atlanta. Engineering Experiment Station
- DOE Contract Number:
- AF33(616)-3879
- NSA Number:
- NSA-13-003838
- OSTI ID:
- 4264877
- Report Number(s):
- WADC-TR-57-662; AD-155516
- Resource Relation:
- Other Information: Project No. 7312. Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- United States
- Language:
- English
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