Methods for inhibiting
corrosion in aqueous evaporative systems where soluble silica (SiO2) is maintained at residuals between 10 Mg / L and saturation, but more preferably maintained at greater than 300 mg / L as SiO2, 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.