Pickling passivation ensures corrosion resistance to components of stainless steel and thus considerably increases their life and usefulness.

The corrosion resistance of stainless steel is due to the presence of at least thirteen percent chromium in the alloy. With oxygen, the chromium forms a dense chemically resistant passive layer of chromic oxide, protecting the surface of the component against corrosion. The passive layer usually forms again after abrasion. The precondition to corrosion resistance and passive layer is a metallically pure surface with a sufficiently high percentage of chromium.

Every mechanical treatment damages the top layer of components i.e.

• Contamination with Ferric matter
• Change in the structure of the layers
• Development of inbuilt stress
• Reduction of chromium content

Heat treatment like annealing and welding leads to scaling and discolouration. This not only deteriorates the appearance of the component but also its corrosion resistance due to the presence of ferric oxides. A continuous passive layer of chromic oxide cannot form here. Hence it is a must to form a metallically pure surface for pickling and passivation.

Corrosive strain on insufficiently Passivated stainless steel leads to :

• Pitting corrosion
• Crevice corrosion
• Stress corrosion cracking
• Intercrystalling corrosion
• Corrosion resulting from contact with foreign metals.

A dense passive layer can only form on metallically pure surfaces. Professionally pickled Passivated stainless steel surface and welding seams:

• Are metallically pure, free of scales and discolouration
• Give the full corrosion resistance of the component
• Have a decorative metallic appearance.

K-2 products of surface innovators are approved by Indian Institute of Technology (IIT) under ASTM-A 380 and ASTM A-967 for pickling & passivation on stainless steel.