De-rouging

Restorative Treatment for Discolored Stainless Steel in High-Purity Systems

Rouging is the reddish-brown discoloration commonly found in stainless steel systems exposed to high-purity water or steam, often in WFI, PW, and clean steam generation systems. It arises from iron oxidation and can compromise visual cleanliness, system validation, and even surface passivity.

AEKS provides specialized chemical de-rouging services targeting:

• Type I (external iron contamination),
• Type II (in-situ passive layer transformation),
• Type III (corrosion and pitting-related rouge)

Our method includes:

• Application of specialized acid blends (e.g., proprietary phosphoric-citric mixtures)
• Temperature-controlled circulation for enhanced chemical efficacy
• Neutralization and post-treatment passivation
• Final rinse with high-purity water (DI/WFI)

Surface inspection is documented with:

• Visual inspection and photography
• Surface iron concentration testing
• Optional TOC, conductivity, and endotoxin testing (if required)

De-rouging is essential for maintaining hygienic standards in GMP manufacturing environments.