Hi Vijay
I have not managed to find any reliable emissivity values for thermal spray aluminium coatings (TSA?), but then I'm not surprised. Emissivity is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. The material type, say aluminium or TSA unfortunately is not the only factor. Temperature, wavelength, surface condition (roughness, oxidation, surface contamination) are big factors.
What is your customer wanting, high or low emissity? What is the application and service conditions for coating? You could alter the emissivity of your TSA, by changing spray parameters, or by post finishing or additive materials like sealers and paints etc.
A few links for you to ponder:
https://en.wikipedia.org/wiki/Emissivity
https://www.x20.org/library/thermal/emissivity.htm
(link dead)/EmissivityTableMetals.htm]EmissivityTableMetals[/url]
http://www.infrared-thermography.com/material.htm
Hope that's of some help