text: Ortho-, pyro-, and tripolyphosphate compounds have been commonly used in detergents (i. e. cleaners) formulations.  For example, see Sodium tripolyphosphate.  Sometimes pyrophosphate, tripolyphosphate, tetrapolyphosphate, etc. are called diphosphate, triphosphate, tetraphosphate, etc., especially when they are part of phosphate esters in biochemistry. They are also used for scale and corrosion control by potable water providers. As a corrosion inhibitor, polyphosphates work by forming a protective film on the interior surface of pipes.