Conformal coating material is applied to electronic circuitry to act as protection against moisture, dust, chemicals, and temperature extremes that if uncoated (non-protected) could result in a complete failure of the electronic system. The coating material can be different depending on conditions. Please refer to following link for more information:
http://en.wikipedia.org/wiki/Conformal_coating

Schneider Electric's 'Tropicalization' process is a conformal coating of silicon spray. It's optional, and to have the meters prepared with a Conformal Coating, the 'Tropicalization' order option has to be requested from the 'Special Order' option of the order form.