rouging

Rouging is a form of corrosion found in stainless steel.{{Cite journal|url=http://www.pharmtech.com/preventive-and-corrective-maintenance-rouge-stainless-steel-equipment|title=Preventive and Corrective Maintenance for Rouge in Stainless-Steel Equipment|last=Rivera, Hadziselimovic, Lopolito|date=2017-02-15|journal=Equipment and Processing Report|series=Equipment and Processing Report-02-15-2017 |volume=10 |issue=2 |access-date=2019-04-12}} It can be due to iron contamination of the stainless steel surface due to welding of non-stainless steel for support columns, or other temporary means, which when welded off leaves a low chromium area.{{cite web|url=http://corrosion-doctors.org/MatSelect/rouging.htm|title=Rouging|website=corrosion-doctors.org}}

There are three classes of rouging: Class I, Class II, and Class III.{{Citation|chapter=Rouging of Stainless Steel in High-Purity Water|date=2006|pages=15–22|publisher=ASM International|isbn=9781627081849|doi=10.31399/asm.hb.v13c.a0004103|title=Corrosion: Environments and Industries}}

Class I – stainless steel surface and the Cr/Fe ratio{{clarify|this term needs to be defined|date=September 2018}} of the metal surface beneath such deposits usually remain unaltered.

Class II – Iron particles originating in-situ on unpassivated or improperly passivated stainless steel surfaces. By their formation the Cr/Fe ratio of the metal surface is altered.

Class III – Iron oxide (or scale) which forms on surfaces in high temperature steam systems. The Cr/Fe ratio of the protective film is usually altered.

References

Category:Corrosion