Printed circuit boards are susceptible to corrosion both from environmental moisture and the voltage that passes through the pins. There are multiple ways to protect an assembled PCB from falling prey to the damage that can be caused from every day use to extend the life significantly of the PCB and overall application.
Protection From Moisture (Humidity)
The best current protection for a circuit board from humidity is to seal the board with a product called humi-seal. This coating is quite light and helps to protect the board and its components from the moisture in the air. It doesn’t fare too well against the board being dropped in water, but then again, rarely do electronics do well when submerged fully in water.
Protection From Voltage
The voltage that passes through the circuit board has the chance to corrode the different components over time. The best product to use when protecting the PCB from voltage is called Conformal Coat. This product does nothing to block out moisture, but does help to reduce the wear and tear caused by the passing of electricity through the printed circuit board. This can be used in conjunction with humi-seal if it is sealing the PCB before the humi-seal is applied, and it is recommended that the two be used together to further protect the circuit board from humidity. Protection from both voltage and humidity help to extend the life of the PCB significantly.
It is important to use products that will help extend the overall life of your printed circuit board in these conditions. For more information, there are plenty of PCB assembly factories that use other coatings to seal the printed circuit boards.