Derouging

On-Site Derouging Services

Whether it is the FDA, NASA or some other external agency – many organizations have mandates to ensure that corrosion (rust or rouge) is not present in their product and distribution systems, tanks, vessels or equipment. Therefore, stainless steel systems for water, steam or products must be free of corrosion. Removing corrosion, also referred to as ‘derouging’, is critical for product safety and also extends the life of systems and equipment. Rouge not only can cause surface degradation, but also expose contaminants into the final product. In addition, rouge areas may exacerbate bioburden issues within the system itself causing greater contamination.

What is Rouge?

A general term used to describe a variety of discolorations in high purity stainless steel systems. It is compose of metallic (primarily iron) oxides and/or Hydroxides. Three types of Rouge are as follows:

Type 1 Rouge

Rouge 1
YELLOW | ORANGE

Originates from an external source. It usually appears as a lightly-adhered red or orange “dusting” of the surface. Most Type 1 Rouge is metal oxide particles that are broken loose by erosion of rouge or cavitation at pump impellers or internals. This type of rouge is relatively easy to remove chemically or by electropolishing. Generally, a wipe may or may not remove Rouge Type 1. However, it is best to passivate the surface after Type 1 rouge removal to ensure Rouge removal.

type 2 rouge

rouge 3
GOLD | RED | BROWN

Forms at the site where it is seen and where chloride exposure is induced. It typically has a red, reddish-orange, or brownish color. A chemical process removes the rouge or it may need more aggressive derouging formulations or by electropolishing. The surface must be passivated after Type 1 rouge removal.

type 3 rouge

rouge 2
GREY | BLACK

Normally contains a form of iron oxide called magnetite, which is black in color and forms in high temperature steam systems. It often has relatively high silica content in many cases which can make it resistant to chemical removal, necessitating the use of more aggressive chemicals. On shiny surfaces, it may appear tightly adhered and shiny, but on rough surfaces, it is less tightly adhered and may have a powdery appearance. Removal of Type 3 Rouge, includes aggressive chemical solution, or mechanical polishing and/or electropolishing.

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Frequently Asked Questions

Derouging is the process of removing rouge, which is a form of corrosion that forms on the surface of stainless steel. Rouge can be iron oxide or other metallic contaminants that compromise the metal’s appearance and performance.

Derouging is crucial for maintaining the integrity and performance of stainless steel equipment. It removes contaminants that can lead to corrosion, biofilm formation, and degradation of the metal surface, ensuring optimal functionality and longevity of the equipment.

Rouge forms due to various factors, including high temperatures, chemical reactions, and the presence of iron particles. It can develop in systems that use steam or water and in environments where stainless steel is exposed to corrosive elements.

There are three main types of rouge: Type I (from water systems), Type II (from high-temperature environments), and Type III (magnetite from steam systems).

Derouging involves the use of chemical treatments to dissolve and remove iron oxide deposits from stainless steel surfaces.

Yes, Astro Pak offers on-site derouging services. This can be beneficial for large or stationary equipment where transportation to an off-site facility is impractical. On-site derouging ensures minimal downtime and disruption to your operations.

 

Yes, derouging removes surface roughness and porosity caused by corrosion, which can assist in preventing biofilm formation. By eliminating these conditions, it reduces the likelihood of bacterial clusters forming on the metal surface.

 

Industries such as pharmaceuticals, biotechnology, food and beverage, and semiconductor manufacturing benefit from derouging services.

Yes, by removing iron oxide deposits, derouging can enhance the performance and longevity of stainless steel systems.

When performed correctly, derouging is safe and effective for most stainless steel surfaces used in high-purity and high-temperature applications.

The frequency of derouging depends on the specific system and its operating conditions, but regular maintenance is recommended to prevent buildup.

After derouging, passivation is typically performed to restore and enhance the protective chromium-oxide layer on the stainless steel surface.

CIP is a cleaning process that removes surface debris and contaminants without disassembling the equipment. Derouging, on the other hand, specifically targets and removes rouge and deeper corrosion products that CIP may not effectively eliminate.