Removal of rouging and blacking

Rouging (ferric oxide) is orange in color and appears on the internal surfaces of austenitic stainless steel (from 40°c) steam or purified hot water production facilities. The principal factors that cause rouging are:

  • Hot water systems, pure vapour, and ozonated water.
  • The presence of ferric ions (solder oxides, lower quality materials…).

Initially, rouging (iron oxide) appears in the passive layer of the material, and when the rouging accumulates under high temperatures it transforms into blackening (magnetite), even more difficult to remove.

Rouging does not appear spontaneously, it always comes from the degradation of an equipment present in the installation. Rouging is unstable and oxidation particles can break off and contaminate possible networks. The stainless steel loses its anti-corrosion properties and its resistance degrades.

Unwinding of stainless steel

Derouging is a dynamic chemical treatment carried out, if possible, under heat followed by passivation. Deblackening is a targeted scouring operation followed by passivation.This process has little effect on the roughness of the treated material.

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