Patent ID: 7862727

Claim:
Method for inhibiting magnesium hydroxide scale formation on structural parts in contact with an aqueous salt containing medium in a desalination system comprising: adding to said aqueous salt containing medium in the system a treatment without acid addition, said treatment comprising (a) a phosphono functional polymer I including a repeat unit of the structure wherein R 1 is H or lower alkyl of from about 1 to 6 carbon atoms and wherein X is OH, or OM wherein M is a cation; and wherein Mw for the phosphono functional polymer (I) ranges from about 500 to 50,000 and wherein the phosphono functional polymer (I) was prepared by aqueous polymerization; b) a maleic-acid based carboxylate containing polymer scale inhibiting agent; and c) a dispersant; wherein said aqueous salt containing medium comprises magnesium cations and hydroxide anions under conditions in which, in absence of treatment, Mg(OH) 2 scale would form on said structural parts; whereby the method inhibits formation of Mg(OH) 2 scale on the structural parts of the desalination system.