20. Corrosion in Waters

All natural and industrial waters are corrosive toward common construction metals if a cathodic process can occur. Oxygen reduction is the most typical cathodic process, for about 95% of dealings, then followed by slightly acidic conditions, the presence of oxidizing species as chlorine and more rarely by bacteria. An important factor that reduces water corrosiveness is the tendency to form protective scales. The main damages due to corrosion are alteration of water quality, especially for drinking water requirements, reduction of components service life, due to wall perforation or other localized corrosion forms, and obstruction inside small pipes due to the high volume of corrosion products. The performance of most used metals are reported with reference to their use in freshwater, brackish and seawater.