| abstract |
Addition of a secondary scale inhibitor is made to a water medium containing a primary phosphonate scale inhibitor to inhibit precipitation of insoluble calcium phosphonates which are formed by the reaction of calcium in the water medium with the primary scale inhibitor thus forming insoluble calcium phosphonate. The secondary scale inhibitor has the function of inhibiting precipitation of such insoluble calcium phosphonates. The secondary scale inhibitor is a copolymer of an acrylic acid and/or methacrylic acid with one or more of a principal comonomer selected from substituted acrylamides, alkoxyalkyl acrylates, substituted and unsubstituted alkyl acrylates, acrylamido alkane sulfonic acids, hydroxyalkyl acrylates, alkyl itaconates, and mixtures thereof. |