The passivation treatment decontaminates the stainless steel from less noble particles such as iron, in this way improving corrosion resistance.
With the passivation treatment the natural passive layer of the steel is restored through a controlled process.
In steel factories, steel is often used with tools contaminated with iron, or steel is stored on iron shelves that give off metallic particles to the stainless steel that bind with its structure, thus losing its anti-rust quality. Steel, with time, can become red stained in the presence of iron and white stained in the presence of aluminum oxides: the passivation process is of primary importance for the longevity of stainless steel and to avoid any surface corrosion phenomena. Passivation is a process of decontamination from iron particles or other oxidizing metals.
Clerici srl has chosen to passivate stainless steel items through immersion.
The bath used is based on HNO3 nitric acid and is suitable for the 300 series. As a reminder, parts not having a clean and contaminated-free surface cannot be passivated, for this reason in the presence of welds it is necessary to first strip the surface by pickling.
As the baths used in the pickling plants are polluting for the environment, Clerici srl is equipped with systems capable of reducing both air and water emissions, complying with the current environmental legislation.
In the case of non-welded materials, such as bent laminations, that are not welded and perhaps satin-finished, the first process will be the degreasing of the piece and then proceed with the passivation. The parts will not undergo color changes and passivation tests will guarantee the successful decontamination of the steel and the restoration to its original layer.
The passivation layer formed is a physical barrier against the exposure of the metal to the external environment by aggressive agents: passivation upgrades stainless steel.
All our passivation processes refer to the American regulation ASTM A380-06 “Standard practice for cleaning, descaling and passivation of stainless steel parts, equipment and systems”.