High stress conditions that aggravate corrosion, scaling and fouling include high pH, high Fe +3 content in cooling water, highly corrosive environment due to high chlorides and low water velocity. These - individually and in combination reduce efficiency of many otherwise acceptable products. Implications of these stress conditions and the best suited products for such applications is:
High pH: Severely affects phosphate based treatment programs. Conventional co-polymer based treatment programs limit pH to a maximum of about 8.3. A slight increase is enough to cause phosphate precipitation.
Aquapharm's MAXINOL range of ter-polymers retain effectiveness up to a pH of 9.2 enabling a) broader operating range, b) reduced corrosion potential by operating at a consistently higher pH and c) reduce or eliminate acid dosing in phosphate based treatment programs.
High Chlorides: Impede formation and repair of passivating films. Molybdates are currently the only effective corrosion inhibitors for such situations. The high cost of molybdates is now a serious concern for such programs. The ability of ter-polymers to stabilize phosphates at a higher pH can be utilized to reduce or even eliminate molybdate dosing for such systems. Treatment programs based on combinations of ortho-phosphate, poly / pyro phosphate with ter-polymers can give acceptable results in high chloride systems.
High Fe +3 content: Heavy metals are known to 'poison' polymers. Co-polymers used as phosphate inhibitors lose more than half their efficacy in presence of Fe +3 . Similar effect is caused by Zn +2 also, considering that zinc salts are used as a part of the treatment, this is can mean either a) poor performance or b) high polymer dosing to get good results.
While bulk water Fe +3 content may not be high (at normal CW pH, most of the Fe +3 will precipitate), the concentration of Fe+3 at the corroding sites will be enough to 'poison' the phosphate stabilizer. Ter-polymers retain their effectiveness even at high Fe +3 levels.
Low Water Velocity: Heat exchangers with shell side cooling, CT basins are typical low velocity areas where accumulation of foulants takes place. In the near static conditions, the dirt, corrosion products and precipitaes settle in this area.
Ter-polymers are able to keep these in suspension even in stagnant conditions for a long time to reduce depositions and fouling.