If a printed circuit board (PCB) is being used in a damp environment, such as outside or in a fridge, it is important to protect it. Lacquer is a thin polymer film that is sprayed or painted onto the PCB and components and this protects it against moisture as well as dust, chemicals and temperature fluctuations.
Many mechanical systems work by moving parts together - this creates friction that, over time, wears the product out. Lubricant is added to allow parts to slide past each other without causing friction and this slows down wear. For example, oil is used as a lubricant for bicycle chains to improve the performance of the bicycle.
Outer casings of electronic and mechanical products can have surface treatments added.