| abstract |
Methods for inhibiting corrosion in aqueous evaporative systems where soluble silica (SiO 2 ) is maintained at residuals between 10 Mg/L and saturation, but more preferably maintained at greater than 300 mg/L as SiO 2 , to provide corrosion inhibiting silica films that protect system metals. Silica is provided by evaporation of water and subsequent concentration and transformation of silica naturally contained in source water. The methods of the present invention provide highly effective inhibition of corrosion for mild steel, copper, stainless steel, aluminum, zinc, galvanized steel and various alloys of such metals. The methods of the present invention comprise pretreatment removal of polyvalent metal ions from the makeup source water, maintenance of concentration of monovalent metal ions, and controlling pH at a minimum of 7.0 in the presence of an elevated temperature aqueous environment. Thereafter, specified water chemistry residual ranges are maintained in the aqueous system to achieve inhibition of scale and corrosion. |