What kind of heat treatment does the passivation of steel belong to?
Passivation is not a heat treatment, but a chemical surface treatment process commonly used on stainless steel and other metals to improve their corrosion resistance. Passivation creates a protective layer against corrosion by exposing a metal surface to a solution containing a specific chemical, usually an oxide or compound.
Specifically, stainless steel passivation is a corrosive improvement process for stainless steel. This process can be divided into the following steps:
1. Cleaning: Before the passivation process begins, the stainless steel surface usually needs to be cleaned to remove grease, dirt and other contaminants to ensure that the passivation solution can fully contact the metal surface.
2. Pickling: Next, stainless steel usually needs to be pickled in an acidic environment to remove iron oxide and other surface impurities, thereby providing a clean surface for passivation treatment.
3. Passivation treatment: After pickling, stainless steel will be immersed in a passivation solution containing chromate, nitric acid and other chemicals. This process results in the formation of a dense, uniform protective layer, usually of chromium oxide, on the surface of the stainless steel. This protective layer reduces the corrosion of stainless steel and improves its corrosion resistance.
The type and effect of passivation can be adjusted depending on the chemical solution and processing parameters used. It is commonly used for stainless steel parts that require long-term exposure to moisture and corrosive environments, such as pipes, valves, food processing equipment, and chemical equipment. This treatment process does not involve high-temperature heating and cooling, so it is different from traditional heat treatment methods.