Corrosion Inhibitors, pH Control, and Alkalinity Adjusters

In addition to water quality control as per the Safe Drinking Water Act (SDWA), the application of chemicals for adjusting pH is one of the main options of internal corrosion control. It should be noted that pH control alone is not sufficient to counter corrosion problems. In such cases, corrosion inhibitors may be used for internal corrosion control. Corrosion inhibitors consist of chemicals that are used in small quantities to counter corrosion. The impact of inhibitors on water quality and their effectiveness 

Selection of corrosion inhibitors is a complex task that depends on many factors. The cost effectiveness of the inhibitor may be obtained from the relationship  

Cost effectiveness = Relative effectiveness x dosage x price per weight. The inhibitor dosage rate depends on the local water conditions and temporal factors, such as the time of the year. It should be quantified in terms of percent corrosion inhibition and extension of useful life. Table 4.29 lists inhibitors used in potable water systems. 

TABLE 4.29 Commonly Used Inhibitors in Potable Water systems (45,46) 

TABLE 430 Costs of Chemicals Used for Corrosion Control (47) 

---