Patent ID: 8148311

Claim:
A cleaning solution comprises a. from greater than 25% to about 50% by weight of an alkyl diphosphonic acid of the basic structure: wherein R 1 and R 2 are either the same or different and select from the group consisting of hydrogen (H), hydroxide (OH), chloride (Cl), alkyl or aryl having between 1 to about 8 carbon atoms and alkyl or aryl amine; b. at least one or more second, acidic compound or mixtures thereof; c. a buffering amount of one or more basic compounds to adjust pH from about 6 to about 10; d. from 0% by weight and up to 5% by weight of a surfactant; and e. water; wherein the mole ratio of alkyl diphosphonic acid to second acidic compound is from about 1:1 to about 10:1.