Reactive chemical cleaning is most often used to improve energy efficiency,
especially on cooling water exchangers and utility boilers. Depending on the type of
foulant, mild to strong acids are circulated throughout the system with inhibitors to
remove the foulants while minimizing impact on the base materials. Care must be taken
not to overexpose the tubes to the chemicals, as metal degradation can occur. After
cleaning, passivation is usually performed utilizing various methods such as an
application of sodium nitrite for carbon steel or an alkaline solution such as sodium
carbonate, commonly referred to as soda ash, for stainless steel.