Basically rust forms on iron containing metals (like your clipper blades and carbon steel scissors) due to the combination of excessive moisture and air (specifically the oxygen in our air). Keep excessive moisture away and oxygen, and your metal iron containing tools won’t rust. Oil on the surface of metal can keep moisture away. Hair wedged between the teeth of your clipper blades and between them can wick away the oil leaving the metal exposed to moisture and oxygen. Clean blades of hair and scale and oil your blades before storing them – best all-around solution no matter if you have a problem or not.
Add a dehumidifier to your shop or storage location – helps all your grooming equipment from clippers to tables preventing rust.
Early rust will clean off easily with an oily rag. WD40 can be used to clean off the rust and give minimal protection. Advanced rust selectively eats at the metal of your blades and scissors causing pits and a rough edge. Pitted rough edges mean the blade may not cut or cut well or long which is why it is important to prevent rust.