CorrosionDOE-HDBK-1015/1-93GENERAL CORROSIONRev. 0CH-02Page 21General Corrosion Summary (Cont.)During the initial fill of a reactor system, great care is taken to promote theformation of the best possible protective corrosion film. The protective film actsas a barrier and stops further uncontrolled corrosion from taking place. Thisprocess, called pretreatment or pickling, involves careful control of reactorcoolant water chemistry and temperature during the pretreatment period.Four methods used to chemically control general plant corrosion are:Passivators (inhibitors) consist of a naturally active metal that corrodesat a very low rate. A common passivator is potassium chromate.Cathodic protection is the external application of an external electriccurrent to the iron so that it acts as a cathode and has no anodic areas.This is accomplished by using either an external electrical source or theuse of a sacrificial anode to provide the electrical current.Removing corrodants to reduce the dissolved oxygen and lesser extentcarbon dioxide. Treating the water in this manner reduces the dissolvedsolids and reduces the conductivity.Chemical addition to alter the chemical reaction or tie up a particularcorrodant. Filming amines, phosphates, and sodium hydroxide are usedto provide organic films and adjust the system pH.The six water chemistry conditions that limit corrosion of aluminum are:Maintaining pH slightly acidic with the value of the pH depending largelyon operating temperature.Elimination of dissolved oxygenElimination of soluble and solid impuritiesPrevention of the introduction of organic impuritiesPretreatment (or pickling)Maintaining water purity
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