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Thermal Emittance

Last updated: October 10, 2017

What Does Thermal Emittance Mean?

Thermal emittance refers to the ratio of the degree of radiant deflection of heat of a given object to that of a standard reference black body. It describes the degree to which a material can radiate the heat it absorbs.


Corrosionpedia Explains Thermal Emittance

Thermal emittance is a dimensionless quantity that is measured on a scale of 0 (a perfect reflector) to 1 (a perfect emitter). Most substances fall somewhere within this numerical range. Thermal emittance has a direct correlation between the light absorbed by a surface and the resulting corrosion. A perfect emitter substance is opaque and emits thermal radiation, thus absorbing any and all light that is projected onto it.

Empirical investigations have shown that a relationship between light and electrochemical cells affect the corrosion rates of metallic surfaces such as carbon steel. Metal objects that are in contact with water and free ions have a higher corrosion rate when exposed to sunlight through a blue filter than when exposed to sunlight through a red filter. Ultraviolet light reacts with metallic surfaces in a manner that accelerates corrosion.



Thermal Emissivity

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