Pickling and Passivation of Stainless Steel
Pickling and passivation are vital to protect stainless steel from corrosion and flaws.
Understanding Stainless Steel Corrosion and Protection
A nice stainless steel surface is spotless, flawless, and free of flaws. Also vital to corrosion resistance is a good surface finish. Stainless steel is protected from corrosion by a passive (protective) chromium oxide layer. When this passive layer is destroyed, the surface becomes active and is no longer resistant to corrosion; it “rusts.”
Stainless steel corrosion can be caused by a variety of surface flaws, such as:
- Heat Affected Zones (HAZ) due to welding
- Weld defects
- Iron Contamination
- Rough Surface
- Organic contamination
- Aggressive chemical
prior to carrying out the passivation and/or pickling process. It’s crucial to clean the surface beforehand. Making sure the surface is clear of grease, oil, grime, and air pollution requires this step.
The Pickling Procedure: Benefits and Recommendations
The pickling procedure (circulation or immersion in INOX Pickling Liquid) eliminates the passive layer and softly etches the stainless steel’s surface. This will ensure that the surface is well cleaned. embedded steel, contaminated by “fremdkorper,” heat tint (HAZ), and weld scale. Because pickling liquid is very corrosive / poisonous and separate pickling processes are necessary for each kind of stainless steel to prevent over-etching. We recommend that these operations be performed by specialized businesses.
Chemical Passivation: Creating and Repairing the Protective Layer
The chemical passivation process (circulation or immersion with INOX Passivation Liquid) is entirely distinct from the pickling process. Instead of eliminating the passive layer, the passivation technique creates or repairs the Cr2O3 (Chromium oxide layer = passive layer) in order to maintain the stainless steel’s corrosion resistance. This technique can be used independently to enrich or maintain the current passive layer or to eliminate surface rust or fly rust.
Re-establishing the Passive Layer with Pickling and Passivation Processes
In order to re-establish the passive layer over the properly cleaned surface, the pickling and passivation processes must be used in conjunction.
Natural vs. Chemical Passivation for Stainless Steel Protection
A clean stainless steel surface forms a passive layer the natural way (with air or ventilation), not always chemical passivation is required after the pickling process.