Study of corrosion and its control in aluminum solar collectors. Annual report, June 1, 1977--July 31, 1978
The development of corrosion control methods for aluminum solar collectors using ethylene glycol heat transfer fluids was studied. Corrosion inhibitors and impurity scavengers have been tested and evaluated at temperatures up to 160 C under various laboratory conditions. A new corrosion rate measurement technique based on the use of thin foil samples was developed and adopted in this program to provide accelerated results. In addition to the development of corrosion control methods, the acquisition of baseline corrosion data was also extended to the aluminum/propylene glycol combination. Propylene glycol was chosen primarily because of its low toxicity. Aluminum corrosion characteristics were determined in 50, 85 and 100% propylene glycol solutions at temperatures between 25 to 160 C. Corrosion behavior of aluminum in more concentrated ethylene glycol solutions (up to 100%) at higher temperatures (up to 160 C) was also obtained in order to broaden the baseline. The cube root pit growth law was also verified experimentally. All the parameters needed to predict the time to plant failure due to pitting perforation were also determined. With regard to the aluminum/propylene glycol combination, aluminum alloys were found to be about ten times more corrosion resistant in propylene glycol than in ethylene glycol solutions under similar conditions. An extensive literature review showedthat phosphates, borates, nitrates and silicates and sodium mercaptobenzothiazole are effective corrosion inhibitors which are compatible with glycol solutions. It was determined that most inhibitor formulas, whether proprietary or prepared in-house, can reduce the overall aluminum corrosion rate to below 1 mpy at temperatures below 100 C.
- Research Organization:
- Giner, Inc., Waltham, MA (USA)
- OSTI ID:
- 6011882
- Report Number(s):
- COO-2934-7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
141000* -- Solar Collectors & Concentrators
ALCOHOLS
ALLOYS
ALUMINIUM
ALUMINIUM ALLOYS
BORATES
CHEMICAL REACTIONS
CORROSION
CORROSION INHIBITORS
CORROSIVE EFFECTS
ELEMENTS
GLYCOLS
HYDROXY COMPOUNDS
METALS
NITRATES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
SILICATES
SILICON COMPOUNDS
SOLAR COLLECTORS