E-mail: authentic013@steelpipes-fitting.com
WhatsApp: +86 13668807131
E-mail: authentic013@steelpipes-fitting.com
WhatsApp: +86 13668807131
Aug. 01, 2025
Pickling and passivation of stainless steel flanges is a key step in the surface treatment process, designed to remove scale, rust, and impurities while enhancing corrosion resistance. The following is a detailed description of the pickling and passivation process for stainless steel flanges:
I. Purpose of Pickling and Passivation
Removing Oxide Layers and Impurities: After welding and heat treatment, a scale forms on the stainless steel surface, affecting its corrosion resistance.
Improving Corrosion Resistance: Passivation treatment after pickling forms a dense passive film on the stainless steel surface, protecting the base material.
Consistent Aesthetics: The flange surface exhibits a silvery-white, uniform metallic luster, enhancing its appearance.
II. Process Overview
Pretreatment
Cleanse the surface from oil and impurities (degreasing agents or alkaline cleaners can be used);
Rinse thoroughly with clean water.
Pickling Treatment
Commonly used pickling solutions: Mixed acids (nitric acid + hydrofluoric acid) or pickling pastes;
Soaking or brushing, the time depends on specific conditions (generally 5 to 30 minutes);
Remove weld marks, scale, rust, etc. Water Washing
Rinse the surface with plenty of clean or purified water to ensure no residual acid.
Passivation Treatment
Use a passivation solution (such as nitric acid or citric acid) to form a dense Cr₂O₃ passivation film on the surface.
Improve the corrosion resistance of the stainless steel and prevent subsequent rust.
Final Rinse and Drying
Rinse thoroughly again.
Dry to avoid water spots or rust recurrence.
III. Precautions
Wear protective equipment during operation and ensure safe ventilation.
This treatment is not suitable for high-concentration hydrofluoric acid treatment of certain austenitic stainless steels (such as 304L).
Ensure that the acid wash is thorough before passivation, otherwise the quality of the passivation film will be affected.
The passivation film cannot be directly observed with the naked eye; however, its effectiveness can be verified through an iron ion precipitation test or a salt spray test. IV. Applications
Stainless steel flanges that have undergone pickling and passivation treatment offer enhanced corrosion resistance and are particularly suitable for use in environments with high hygiene requirements or high corrosive environments, such as:
Food processing equipment
Pharmaceutical piping systems
Chemical piping projects
Offshore facilities
Cangzhou Aosendic Pipe Fittings Manufacturing Co., Ltd. is a large-scale manufacturer specializing in the production of elbows, tees, reducers, elbows, and caps. We comply with ASTM, ANSI, JIS, DIN, GB, and other standards, covering virtually all steel types.
Please contact us for any purchasing inquiries or questions.
Mobile: 86-13668807131
Website: https://www.authenticfitting.com/
Address: Mengcun Hui Autonomous County, Cangzhou City, Hebei Province
Email: authentic013@steelpipes-fitting.com
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Authentic is here to help you find the right pipe fittings and flanges for your specific needs.
FAQ
What certifications do your products have?
Our products comply with international standards such as ASTM, ANSI, JIS, DIN, and GB. We also hold various certifications to assure quality and reliability, including ISO 9001.
How can I get some samples?
If you need, we will offer you samples for free, but new customers are expected to pay express charge.
To which country have you supplied your products?
We have supplied to Thailand, China Taiwan, Vietnam, India, South Africa, Sudan, Peru, USA, Brazil, Trinidad and Tobago, Kuwait, Qatar, Sri Lanka, Pakistan, Romania, France, Spain, Germany, Belgium, Ukraine etc. (Figures here only include our customers in latest 5 years.)
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authentic013@steelpipes-fitting.com
+86 13668807131
Donghe Industrial Zone, Mengcun County, Cangzhou City, Hebei Province
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