Following my articles about the pig-leg dehairing machine, hereby a short update of the progress:
All welding compositions for the dehairing machine are ready now. All stainless steel parts must now be treated through staining (pickling).
Staining (pickling) after the construction phase removes chromium depleted zones and foreign iron, restores corrosion resistance and brings it back to the original level of the base material.
As a result of heat input, for example during welding, there is a discoloration caused by oxidation of the material and an excessively thick oxide skin and a chromium depleted zone. These locations offer considerably less resistance to local corrosion (chloride pitting corrosion).
In addition to the loss of corrosion resistance due to heat input, this can also be caused by iron contamination. Iron contamination of the stainless steel surface can occur as a result of sanding, grinding, setting and the like with material (tools) of carbon steel or tools that are also used for the processing of carbon steel. Contamination often occurs during handling and transport of the material.
As an experienced machine builder for the intestinal processing industry Holdijk Haamberg GmbH chooses this surface treatment because of the transparency of its products and with a view to the long term. With a stained surface, all welds remain visible so that our products maintain their robust appearance and exhibit a high degree of craftsmanship. In the long term of use, a stained surface in practice remains much nicer than, for example, a blasted surface. The pores of the surface are nicely sealed so that it remains very easy to clean and retains its beautiful, smooth appearance.