Stainless steel could corrode in service if there will be contamination right off the surface. Picklel Passivation is a type of chemical treatment that is being applied right towards the surface of stainless steel in order to remove contaminants and at the same time help in the formation of continued chromium oxide. Passivation and pickling are two types of acid treatments and none of them can remove grease or oil. If the process of fabrication will attract a lot of dirt, it will be necessary to make use of detergent and alkaline right before the passivation and pickling.
Pickling is basically the process of removing high temperature scale as well as any adjacent low chromium layer of metal off the surface of stainless steel through a chemical process. Where steel is being heated by means of welding, heat treatments and other means, to a point where the colored oxide layer will be seen, there will be a chromium depleted layer that will be found on the surface of the steel right below the oxide layer. The lower chromium content will provide lower corrosion resistance. In order to restore the most excellent corrosion resistance, the damaged metal layer should first be removed in order to expose a fully alloyed surface. The process of mechanical removal could leave abrasives as well as other particles embedded, and thus, chemical process is being employed by means of Picklel Passivation.
Passivation is the process of treating surface of stainless steel, which is usually done by means of an acid solution or paste in order to remove contaminants and to encourage the formation of passive film to a freshly created surface.
The usual passivation treatment will also include nitric acid solutions and pastes that will clean off the steel surface and free it from iron contaminants. Utmost care should be taken in choosing and using passivation treatment in order to ensure that the chosen treatment will target the contaminants. Picklel Passivation also helps in the rapid development of the passive oxide film right on the steel’s surface. Passivation will not usually result to a marked change on the appearance of the surface of the steel.
Heat treatments such as welding and annealing will usually lead to discoloration and scaling. This will not only cause deterioration on the appearance of the component but also its ability to be corrosion resistance as a result of the presence of the ferric oxides. The continuous passive layer of the chromium oxide will not be formed here, and thus, it should be metallically clean and must be a pure surface by pickling right before the passivation.
The process of Picklel Passivation makes use of dangerous acid that could trigger damage on the environment as well as on the operator, if the process is not handled well. The stainless pickling is highly corrosive to carbon steel. The process makes use of strong acids and the usual precautions to safety must be adhered to. It is a good idea to consult the materials safety data sheet as well as the product packaging for a more detailed advice when it comes to Picklel Passivation.