Derouging
Derouging Services
Rouge – also referred to as staining in the Food & Beverage (F&B) industry – is a general term used to describe various discolorations in high-purity stainless steel systems. It is composed of metallic oxides and/or hydroxides, primarily iron. Many organizations and industries have mandates to ensure that corrosion, such as rust, rouge, or staining, is absent from their product and distribution systems, tanks, hoppers, vats, and equipment. Consequently, stainless steel systems used for water, steam, or products must be free of corrosion. Removing corrosion, a process known as ‘derouging’ or ‘de-staining’ in the F&B sector, is essential for product safety and extends the lifespan of systems and equipment. Rouge not only causes surface degradation but can also introduce contaminants into the final product. Additionally, rouge can exacerbate bioburden issues within the system, leading to greater contamination. There are three general types of rouge:
Type 1
“Type 1” rouge (staining) originates from an external source and typically appears as a lightly-adhered red or orange “dusting” on the surface. Most Type 1 rouge consists of metal oxide particles that become dislodged due to erosion or cavitation at pump impellers or internal components, including tanks, hoppers, and vats. This type of staining is relatively easy to remove (de-stain) through chemical cleaning or electrolytic cleaning. While wiping may or may not effectively remove Type 1 rouge, it is advisable to passivate the surface after removal to prevent further corrosion.
type 2
“Type 2” rouge (staining) forms at the site where it is observed and where chloride exposure has occurred. It typically exhibits a red, reddish-orange, or brownish color. Removing Type 2 rouge requires chemical processes or more aggressive derouging (de-staining) formulations, or alternatively, electropolishing. After removing Type 2 rouge, the surface must be passivated to prevent further corrosion.
type 3
“Type 3” rouge (staining) typically contains a form of iron oxide known as magnetite, which is black in color and forms in high-temperature steam systems, including those found in F&B hoppers and vats. It often has a relatively high silica content, making it resistant to chemical removal and necessitating the use of more aggressive chemicals. On shiny surfaces, it may appear tightly adhered and shiny, while on rough surfaces, it is less tightly adhered and may have a powdery appearance. Removing Type 3 rouge involves aggressive chemical solutions, mechanical polishing and/or electropolishing.
ON-SITE
Whether you’re conducting a planned shutdown or require emergency response, Astro Pak can mobilize crews from one of our nationwide locations to your facility, utilizing a modern fleet of service vehicles, pump skids, and our chemistries and processes. We provide derouging, passivation, surface finish, and a wide range of chemical cleaning services, circulating our chemistry through your systems and equipment.
SHOP
For components, parts and sub-systems that can be cleaned out-of-place, our shops are well suited to meet your cleaning and passivation requirements. Our nationwide shop facilities deliver prompt and reliable service and features state-of-the-art equipment that can accommodate hardware of all sizes and volumes. We have dip tanks up to 40ft and overhead bridge cranes with 10 ton lifting capacity for oversized parts.
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Resources
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A recurring myth in some industries is that “rouge is a protective layer” that enhances, rather than degrades, stainless steel’s durability. This mistaken belief is primarily based on certain types …
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.
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.
That depends upon the quality level desired and the sensitivity of the product process to low levels of iron or iron oxides. It also depends upon the methods used to refine the final product, including filtration, evaporation/drying, or iron’s effect on the biotech process. Generally, lightly discolored wipes or faintly visible rouge is acceptable, distinctly colored wipes or significant surface discoloration is unacceptable. Use of filtration testing to measure the amount and size of particles in the process fluids can be used as a guide to evaluate the effect of rouge coming off the surface.
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.