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http://dx.doi.org/10.14773/cst.2019.18.5.182

Corrosion Resistance and Thermo-optical Properties of Lithium Polysilicate Spray Coated Anodized AZ31B Magnesium Alloy for Space Applications  

Ghosh, Rahul (Thermal Systems Group, U R Rao Satellite Centre, Indian Space Research Organization)
Thota, Hari K. (Thermal Systems Group, U R Rao Satellite Centre, Indian Space Research Organization)
Rani, R. Uma (Thermal Systems Group, U R Rao Satellite Centre, Indian Space Research Organization)
Publication Information
Corrosion Science and Technology / v.18, no.5, 2019 , pp. 182-189 More about this Journal
Abstract
A thin spray coating of inorganic black lithium polysilicate (IBLP) on black anodized AZ31B magnesium alloy was fabricated for better corrosion resistance and thermo-optical properties for thermal control of spacecraft components. The morphology of the specimens with and without IBLP-based spray coating was characterized by SEM-EDS techniques. Impedance and potentiodynamic measurements on the specimens revealed better corrosion resistance for the specimen with a thin coating of lithium polysilicate. This was primarily due to the presence of lithium polysilicate inside the micro-cracks of the black anodized specimen, restricting the diffusion paths for corrosive media. Environmental tests, namely, humidity, thermal cycling, thermo vacuum performance, were used to evaluate the space-worthiness of the coating. The thermo-optical properties of the coating were measured before and after each environmental test to ascertain its stability. The specimen with an IBLP-based spray coating showed enhanced thermo-optical properties, greater than ~0.90. Hence, the proposed coating demonstrated better handling, better corrosion resistance, and space-worthiness during the pre-launch phase owing to its improved thermo-optical properties.
Keywords
Potentiodyamic polarization; Impedance spectroscopy; Magnesium alloy; Coatings; Lithium polysilicate;
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