Pickle Passivation of Stainless Steel Products
Pickle Passivation helps to ensure corrosion resistance to the components of stainless steel and helps to considerably influence their life as well as their usefulness. The corrosion resistance of steel is often due to the presence of about thirteen percent chromium on the alloy. As for the oxygen, the chromium will form a dense chemically resistant layer of the chromic oxide that keeps the surface protected against any kind of corrosion.
Mechanical Treatment Damages on the Layer of Components
The passive layer of Pickle Passivation often forms again right after abrasion. The precondition to the corrosion resistance as well as passive layer is usually a metallically pure surface that has a sufficiently high presence of chromium.
Each and every mechanical damages of the top layer of the components are the following.
• Contamination of the Ferritic matter.
• Change in the structure of the layers.
• Development of in-built stress.
• Reduction of Chromium.
This will not only deteriorate the appearance of components but its corrosion resistance as well because of the presence of the ferric oxides. The continuous Pickle Passivation will not form from here, but instead, it is important that you will have a clean and pure surface by means of pickling right before passivation.
Corrosion Strain on the Stainless Steel
The corrosion strain off the insufficiently passive stainless steel can lead to the following.
• Pitting Corrosion
• Crevice Corrosion
• Stress Corrosion Cracking
• Inter Crystalline Corrosion
• Corrosion that results to a contact with foreign objects
A dense passive layer will only be formed on the metallically pure surfaces. The Pickle Passivation that is done well for a stainless steel surface and welding seams is the following.
• Metallically pure and free from discolouration and scales.
• Consists full corrosion resistance on the components and consists of decorative metallic appearance.
Pickling versus Passivation
Pickling makes use of more aggressive acid as compared to those that are being used for passivation. The chemicals used for pickling of the stainless steel are well capable of dissolving the oxidation, weld oxides as well as scale and is well capable of etching the base material. Passivation, on the other hand, is more suitable to components that are free scale as well as the existing oxides. The newly machined components of the typically passive and the pickling is well suitable for new or for used materials that are welded, heat treated, cast or exhibit the existing oxides.
While the Pickle Passivation is intended to take off the free iron as well as surface contaminates, it is not effective at removing the existing oxidation, scale, weld oxides, scale as well as heavy contaminates. Both Passivation and Pickling is being used together on equipment in removing the oxidation, which helps to improve the corrosion resistance and as such, extends the life as well as the overall value of components. The chemical passivation is cleaner and is a more subtle process. The passivation chemicals that are used are not really aggressive in order to dissolve the surface oxides and thus, the pickling might be used before or in lieu of the passivation.