PICKLING & PASSIVATION
Pickling is the removal of a thin layer of the stainless steel surface in order to remove all impurities from stainless steel surfaces with the objective of preserving a pure metal surface. The protective passive layer can only be formed on such pure metal surfaces. During the process iron particles and chromium carbides - which are present in the material - are removed by using an acid mixture of nitric acid and hydrofluoric acid.
Passivation means forming the protective passive layer. This can 'grow' the natural way with humidity and oxygen or with demineralized (oxygen-rich) water. However, as there is a risk of corrosion until the formation of the passive layer is restored, it is recommended that passivation is done by using chemicals as this process will only take a few minutes instead of days.
H2Ofinish & Pickling
A perfect match
Spray or tank?
TANK IMMERSION or SPRAY PICKLING
The pickling can be carried out in various ways; tank immersion pickling or spray pickling. The type of pickling depends on size and type of construction. For smaller and closed objects, the choice is often made for immersion (full bath). The larger and open objects that cannot be immersed are being pickled by means of pickled mist (spray pickling).
VIDEO: THE RESULT
This video was made just a few minutes after pickling and passivating these large containers at our workshop. Size of the objects to be treated is not a problem as we have a spacious fully self-contained area available for pickling and passivating. Pickling is the process used to remove weldheat tinted layers from the surface of stainless steel fabrications, where the steel’s surface chromium level has been reduced (as can also be seen on the video, showing an even coloured stainless steel surface).