Corrosion Resistance of Metallic Solar Absorber Materials in a Range of Heat Transfer Fluids. Final Technical Report

摘要

The work described in this report is intended to provide manufacturers, designers, and installers with reliable corrosion compatibility data, meaningful maintenance schedule, and confidence in durability and performance of solar collector units. The corrosion behavior of Cu alloy 122, Al alloy 1100, mild steel 1010, and a ferritic stainless steel (alloy 444) was determined in a variety of potential solar heat transfer fluids. The fluids included potable waters, water glycol solutions, and four non-aqueous fluids. The test apparatus cycled the temperatures of the fluids through those typical of an operating solar energy collector unit. The 444 stainless steel was the most corrosion resistant material and in uninhibited solutions demonstrated only extremely shallow pits during the 180 day test. The use of inhibited solutions generally prevented pits from forming. Cu alloy 122 showed quite low corrosion rates in uninhibited solutions although the presence of excess solder flux promoted some crevice corrosion. In such solutions, uniform, corrosive attack produced general surface roughening along with a protective surface oxide. The overall corrosion rate of the alloy was generally lower in inhibited glycol solutions although pitting within the crevice region occurred in limited cases. Exposure in the non-aqueous fluids resulted in extremely low corrosion rates with little evidence of localized attack. (ERA citation 10:011055)