The Treatment of the BMW 801D-2 Radial Aero Engine Rescued From the Loiret River. | |||||||||||||
TREATMENT PLAN & DISCUSSION | |||||||||||||
A detailed theoretical explanation of the treatment of composite objects made up of aluminium and iron alloy have been discussed in detail elsewhere.1 However it is necessary to outline some basic theory behind the treatment plan. Necessity of the treatment.
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Treatment conditions.
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Thus an experimental Potential – pH diagram can now be constructed, modified to the required conditions. A “protection” area now appears in the region which is suitable for dechlorination treatments. (fig. 15). It was anticipated that the treatment procedure would generally follow that which has already been adopted in Australia for the treatment of the Pratt and Whitney “Twin Wasp” engine. The BMW engine, having been rescued from a freshwater environment, had the appearance of being in a far less corroded condition when compared to the Pratt and Whitney, which was recovered from sea-water and had been left exposed to the atmosphere untreated for some 20 years. Obvious signs of corrosion due to chloride contamination were absent on the BMW engine itself, although some of the smaller parts which were salvaged at the same time manifested typically blue/green colouration of Al/Cu alloy corrosion products. A thin layer of corrosion products and concretions were apparent on both iron and aluminium components (fig. 16.). |
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Notwithstanding, a decision was made to conduct the treatment according to the following global plan: 1. Pre-cleaning.
2. Pre-treatment.
3. Removal of iron concretions using cathodic polarization.
4. Removal of the silicates from the metal surfaces.
5. Dechlorination of the object using cathodic polarization.
6. Citrate decontamination.
7. Finishing Treatments.
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[1]
Degrigny, C.'Mise Au Point D'un Traitment Cathodic De Stabilisation De Pieces
En Alliages D'Aluminium Degradees Par Corrosion En Miliue Aqueux'. These
de Doctorat L'Université Paris VI. 20 Nov. 1990. [2] Unpublished results obtained from experimental work conducted at AWM and Valectra. |
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