Stainless Steel Pickling
Transflow (Scotland) Ltd
At Transflow (Scotland) Ltd, we have extensive experience in pickling a wide variety of equipment fabricated from all grades of Stainless Steel, including Duplex and Inconel625, and cleaned to ASTM A380, A967 standard or client’s specific requirements.
Stainless Steel Pickling is a process used to remove impurities, such as stains, oxidation, and other forms of corrosion, from the surface of stainless steel. It involves using a pickling solution, typically a mix of acids, to clean and restore the metal to its original state. This is often necessary for stainless steel after processes like welding or heat treatment, which can leave oxides and scale on the surface.
Stainless steel pickling is widely used in industries like Pharmaceuticals, Nuclear, Distillery, Ship Building and Food Processing to ensure the steel maintains its performance and aesthetic properties.
Pickling typically involves the use of a nitric acid and hydrofluoric acid or ammonium bifluoride solution, which works by removing a microscopic layer of stainless steel along with the contaminants. This ensures that the stainless steel surfaces are clean and free from corrosion byproducts.
To achieve the best results, Degreasing is typically performed before pickling, ensuring that all oils and contaminants are removed. Following pickling, a passivation stage is essential to replenish the chromium oxide layer and restore the stainless steel’s corrosion-resistant properties.
Stainless Steel Passivation
Transflow (Scotland) Ltd
Stainless steel is naturally protected against corrosion by the formation of a passive layer, primarily composed of chromium oxide. However, this protective layer can be compromised through processes such as cutting, welding, heating, grinding, or exposure to certain chemicals. Once disrupted, the stainless steel becomes vulnerable to corrosion.
Passivation is the process of restoring this protective chromium oxide layer. This is achieved by treating the stainless steel with strong oxidizing agents like nitric acid or chelating agents such as citric acid, which re-establish the integrity of the passive layer.
At Transflow (Scotland) Ltd we bring over 22 years of expertise in passivation using both nitric and citric acid, serving clients in the UK and internationally. We follow rigorous industry standards, including ASTM A380, A967 or client’s specific requirements. Our experience spans a wide range of equipment, with specialized knowledge in the passivation of various Pipework, Castings, Flanges, Breather Tubes, Injectors (Bullhorns), Tanks & Vessels which we carefully evaluate to ensure the most effective passivation process.
After completing the initial procedures, TSL can proceed with the following test procedures:
Ferroxyl Test, Passivity Test, Salt Test, PH Test and Conductivity Test.
By carrying out these tests, TSL can assess the corrosion resistance of materials and coatings, evaluate environmental conditions that may affect their durability, and determine their overall performance in various real-world scenarios.
