Colloidal silica (SiO2) is perhaps the most undesirable inorganic deposit formed in industrial water treatment systems. SiO2 can either be found in bulk or on surfaces, such as heat exchangers, pipelines, or membrane. Conventional mineral scale inhibitors cannot inhibit its formation. Chemical cleaning is difficult and not free from hazards. This paper reports the excellent inhibition efficiency of adipic acid/amine-terminated polyethers D230/diethylenetriamine copolymer (AA/AT/DE). However, a small amount of silica-AA/AT/DE white insoluble floc appears in the solution. To overcome this problem, poly-epoxysuccinic acid (PESA) is introduced. PESA by itself cannot inhibit silica polymerization. However, the combination of PESA and AA/AT/DE cannot only prevent the white floc, but also improve the inhibition performance of AA/AT/DE. The underlying mechanism is investigated based on zeta potentials and atomic force microscopy topography. (C) 2011 Elsevier Inc. All rights reserved.