Derouging

Principle:

The rouging of stainless steel installations is the result of the formation of iron oxide, hydroxide or carbonate from external sources or related to the destruction of the passive layer of stainless steel. The colour variation depends on the type of oxide formed and the variation in water associated with the corrosion process. The colours vary from orange to black.

In purified water systems, the rouge can be classified into three types:

• Type I: related to contamination from external sources, usually the erosion of pump parts, for example
• Type II: induced by the presence of chloride on the surface of the stainless steel
• Type III: the colour changes to black here and is present in high temperature steam facilities.