  In this article we report the atypical and anomalous evaporation kinetics of
saline sessile droplets on surfaces with elevated temperatures. In a previous
we showed that saline sessile droplets evaporate faster compared to water
droplets when the substrates are not heated. In the present study we discover
that in the case of heated surfaces, the saline droplets evaporate slower than
the water counterpart, thereby posing a counter-intuitive phenomenon. The
reduction in the evaporation rates is directly dependent on the salt
concentration and the surface wettability. Natural convection around the
droplet and thermal modulation of surface tension is found to be inadequate to
explain the mechanisms. Flow visualisations using particle image velocimetry
PIV reveals that the morphed advection within the saline droplets is a probable
reason behind the arrested evaporation. Infrared thermography is employed to
map the thermal state of the droplets. A thermosolutal Marangoni based scaling
analysis is put forward. It is observed that the Marangoni and internal
advection borne of thermal and solutal gradients are competitive, thereby
leading to the overall decay of internal circulation velocity, which reduces
the evaporation rates. The theoretically obtained advection velocities conform
to the experimental results. This study sheds rich insight on a novel yet
anomalous species transport behaviour in saline droplets.
