The phenomena of rouging, which is named after the rouge used by women, mostly occurs in hot ultra-pure water systems and clean steam systems. Water with a very low ion content must be expected to exert a strong “suction” effect on components of the material alloys, generally stainless steel, and therefore reduces their ion shortfall. As the temperature increases, the shift in the carbon dioxide equilibrium causes the pH value to be reduced and brings about a reduction of the electro-chemical potential through oxygen poverty. These phenomena result in a change in the thermo-dynamic equilibrium causing the passive film to weaken. Even ozone treatments promote the formation of thin rouging layers. However even in storage containers for CIP solutions (NaOH or KOH solutions) discolouring in the passive layer has been observed. If, for example, the rouging in pure steam systems is not removed from time to time, then blacking could occur. With increasing time pollution with small particles out of these layers cannot be excluded.

- Typical discolourations

- Values based on our own experience

- Rouging in literature

- Removing rouging