CORROSION INHIBITING BEHAVIORS OF SILICA IN ZERO LIQUID DISCHARGE (HIGH TDS COOLING WATER) USING REAL TIME CORROSION MONITORING TECHNIQUES

Corrosion rate studies were conducted in the laboratory on high total dissolved solids (TDS), zero liquid discharge (ZLD) cooling water. The cooling water had been treated with silica corrosion inhibitor chemistry in the field operating system. Corrosion rates were measured using real time coupled multi-electrode array sensor technology. The study evaluated both general and localized (pitting) corrosion rates for carbon steel (CS), copper, aluminum, zinc and stainless metals at temperatures ranging from 77 to 190oF (25 to 88oC). The study confirmed that the silica chemistry provided exceptional corrosion inhibition with very low corrosion rates (i.e., < 0.3 mpy [0.0076 mm/yr] on1008 CS) for mild carbon steel at high TDS and temperature extremes, as well as exceptionally low corrosion rates on other metals evaluated. The laboratory study corroborated field corrosion results, and established this procedure as a potentially efficient means of predicting corrosion inhibitor performance with various metals and water temperatures in field systems with given system water chemistry and inhibitor residuals. The “Green Chemistry ” corrosion inhibitor evaluated was silica (SiO2) which is controlled at concentrations between 200 mg/L and saturation, typically greater than 300 mg/L as soluble SiO2, provided through evaporative concentration and conversion of natural silica in the source water