Study of the Microstructure, Corrosion and Optical Properties of Anodized Aluminum for Solar Heating Applications

Humans are increasingly required to harvest green solar energy in order to reduce energy bills and save the environment from the excessive use of fossil resources. In this article, the microstructures of both commercial non-colored anodized Al and commercial blackened anodized Al were studied using optical and scanning electron microscopy in order to interpret the results of their use as solar absorbing surfaces. Microscopic examination showed that the thickness of the anodization layers of the non-colored anodized Al and the blackened anodized Al were approximately 11 mu m and 14 mu m, respectively, and they were perfectly adhered to the mother Al. The corrosion rate of all studied Al surfaces was investigated using the potentiodynamic polarization technique in 3.5% NaCl as the corrosive medium. The blackened anodized Al surface exhibited the highest corrosion resistance, which made it the best surface for solar heating systems. Moreover, raw Al, matte black painted Al, and blackened anodized Al were tested as selective surfaces for solar radiation in different weather conditions. Our results demonstrated the superiority of the blackened anodized Al in terms of the ability to absorb solar radiation, in addition to its higher corrosion resistance properties. In experimental testing, temperature values higher than 90 degrees C were reached several times. A gain of an extra 5 degrees C was achieved when using a double-glazed cover in comparison with a single-glazed setup. In conclusion, we highly recommend using a commercial blackened anodized Al surface to manufacture solar absorbing heaters, owing to its similarity in solar radiation absorptivity with the commercial matte black painted Al, excellent corrosion resistance, superior endurance upon long-term exposure to solar radiation, light weight, low price, and availability. Additionally, the light reflectance % test demonstrated the characteristics of the used solar selective surfaces.

Automated summary

This study examines the microstructures and corrosion resistance of commercial non-colored anodized aluminum and commercial blackened anodized aluminum as solar absorbing surfaces. The results indicate that the blackened anodized aluminum exhibits superior solar radiation absorption and corrosion resistance properties. Experimental testing also demonstrates the advantages of using a double-glazed cover in solar radiation collection compared to a single-glazed setup.