The protective layer of chromium oxide in the stainless steel can be damaged during processing, or get an unfavourable composition. This can happen, for example by welding (discoloration of the material), heat or mechanical operations. These effects reduce the corrosion resistance and make the material less attractive. Both effects are recoverable with chemical or mechanical treatments or a combination.

Chemical treatment. The material is brought into contact with a stain, whose active substances consist of 22% nitric acid and 5% hydrogen fluoride, and done by dipping in liquid stain or apply using brush or spray in gel-form. The process consists of four steps: 

  • Degreasing
  • Pickling
  • Rinse
  • Passivation

For mechanical treatment, there are four methods:

  • glass Pearl blasting
  • sanding
  • grinding
  • brushing