Abstract
Stabilized phosphate cooling water programs have been exceptionally effective and well established in the marketplace for close to twenty years. Identification of this technology allowed chromate to be eliminated from open recirculating systems, providing less toxic operating conditions. However, very good control of stabilized phosphate applications is necessary in order to ensure chrome-like corrosion and deposit control performance. Difficulties with stabilized phosphate technology have occurred when it is used along with chlorine. Elevated chlorine dosages are sometimes necessary for microbial control. When this occurs, copper induced pitting becomes a concern as does the degradation of the cooling water program itself, i.e. phosphonate reversion. New programs have been identified which maintain their component integrity in the presence of chlorine. They offer improved deposit control performance under a variety of stressed cooling water conditions by using select polymer blends, as opposed to a single polymer. They also incorporate a new azole corrosion inhibition chemistry which minimizes copper-induced pitting associated with over-chlorination. Laboratory and field experience with this technology is discussed.
