Staining and passivation: an essential post-treatment for stainless steel
Stainless steel is an alloy consisting mainly of iron, chromium and nickel, supplemented with other elements and impurities. During production processes, these impurities can form carbides, causing the stainless steel to lose some or all of its corrosion-resistant properties.
Furthermore, mechanical polishing, milling, turning, machining, welding and other heat treatments can compromise the original austenitic structure. This reduces the stainless steel’s ability to spontaneously form a protective oxide layer.
It is therefore necessary to chemically remove impurities, oxides and embedded iron particles from stainless steel structures following these operations. This is best achieved by pickling in a carefully formulated mixture of acids. Under the action of these pickling acids, impurities, weld discolouration and embedded iron particles lose their adhesion to the base material. Pickling is followed by a carefully designed rinsing procedure.
During passivation, a protective, dense and well-adhering oxide layer forms. This oxide layer restores the material’s natural corrosion barrier.
Through pickling and passivation, the stainless steel regains its original properties. The material’s original smoothness is virtually preserved. The stainless steel acquires an attractive, even, satin-grey finish.
Packo Surface Treatment pickles and passivates stainless steel in accordance with virtually any required standard or procedure, including ASTM, MIL, MIT, DIN, ISO, EN, etc.
A corresponding certificate can be requested.
Depending on the material, dimensions and required specifications, you can choose from immersion pickling, spray pickling, localised pickling, anodic pickling, mechanical pickling, acid-free pickling, eco-friendly pickling, etc.
Both small parts and large structures weighing up to approximately 10 tonnes can be treated, with a lead time ranging from 1 day to just over a week, depending on the required and available capacity. For immersion pickling, Packo has baths with net dimensions of approximately 7 × 2 × 2 metres.
Chemical product for own application
Processing in our workshop offers you the advantage that no chemical contamination is left behind in your workshop or on site. With us, there is also no risk of iron contamination, and the procedure involving chemical products is carried out under strict supervision.
If it is nevertheless difficult to bring the parts to us or to carry out preventative maintenance, we offer Passivinox F300 in containers of at least 5 litres: an acid cleaner, rust remover and passivator for stainless steel.
Our technicians are available to provide advice and recommendations for use, whilst ensuring compliance with safety regulations.
