Scaling is the deposition of dissolved matter from a liquid on a (usually hot) surface. A well-known example is scaling in boilers.
This scale forms a layers that reduces the heat transfer coefficient and therefor gives big energy losses. Also it can lead to a higher flow resistance (because the inner diameter of tubes gets smaller); this is also gives energy losses and a shorter life time of pumps or compressors.
More over you have to remove the scale by hand after a certain time. Besides the cleaning costs themselves, you will also have stand-still of machines and/or heat-exchangers.
Filtermat Holland has two products in its delivery program that prevent or limit the deposition of scale strongly.