Batteries should be kept clean at all times. If installed or stored in a dirty location, regular cleaning should be performed. Before doing so, assure that all the vent caps are tightly fastened. Using a solution of water and baking soda (100g per litre), gently wipe the battery and terminals with a damp sponge, then rinse with water.  Remove corrosion buildup from terminals and connections with a wire brush, re-apply a dielectric grease and torque connections as recommended.

Batteries and terminals should be cleaned any time they are removed/added/moved or noticeable corrosion or excessive heat is noted a battery.