Methods for inhibiting scale formation

A liquid additive for inhibiting the precipitation of scale forming compounds from aqueous solutions consisting essentially of a mixture of a homopolymer of acrylic acid wherein about 70% of the active hydrogen ions are replaced by sodium ions, said polymer having an average molecular weight in the range of from about 1,000 to about 10,000, and a water-soluble organic cationic surface active compound selected from the group consisting of:

• a primary alkylamine acetate having the following formula ##STR8## wherein R.sub.6 represents an alkyl radical having from 8 to 18 carbon atoms,
• a quaternary ammonium compound having the following formula ##STR9## wherein R.sub.8 represents hydrogen or an alkyl radical having from 1 to 20 carbon atoms, R.sub.9 represents a benzyl radical and X represents a halide, and
• mixtures of said compounds wherein said water-soluble organic cationic surface active compound is present in said additive in an amount substantially equal to the neutralization equivalent of said acrylic acid polymer.