Mineral scales are formed in cooling water systems and they cause heat transfer problems. Much research has been carried out to reduce the carbonate and sulphate scales of calcium. To inhibit the scale formation in cooling water systems, vinyl acetate-acrylic acid (VA-AA) and vinyl acetate-methacrylic acid (VA-MAA) copolymers were synthesized, characterized, and the ability of the polymers to mitigate the calcium carbonate and calcium sulphate scale formation was tested through chemical screening, constant potential electrolysis, and electrochemical impedance techniques. XRD (X-ray diffraction) and SEM (scanning electron microscope) studies were performed to understand the morphological changes of the scales in the presence of the polymers. The biocidal, gelation, and iron dispersion ability of the polymers were also noted. Among the two threshold inhibitors, VA-AA shows slightly better antiscaling properties even at higher temperatures and pH for both CaCO3 and CaSO4 scales compared to the methacrylic copolymer. (c) 2005 Wiley Periodicals, Inc.