Passivation Of Stainless Steel Pipe

Corrosion resistance is the primary performance of stainless steel and stainless steel pipes that distinguishes them from other steel types and ordinary steel pipes. The corrosion resistance of stainless steel depends on its chemical composition, surface condition and environmental conditions. Under specific conditions of use, that is, after the steel type and environmental conditions are determined, the prerequisite for ensuring corrosion resistance is to form a uniform and dense passivation film on a clean and smooth surface, and the local destruction of the passivation film is the root cause of local corrosion. reason.

Characteristics of the formation of passivation film: The passivation film formed on the surface of stainless steel at room temperature is not a "real" oxide film, and its physical and chemical structure has not yet been fully confirmed. It is commonly known as composite oxide or hydrogen oxide film. The passivation film formed spontaneously on the surface of pure stainless steel in the atmosphere or other oxygen-containing environment has self-healing properties. Room temperature, purification and aerobic environment are three important concepts or elements for the formation of passivation film. Stainless steel pipes and all stainless steel products are subject to purification or passivation treatment before leaving the factory to form a purification film on the surface to ensure their corrosion resistance.

Contamination and damage of the passivation film: The passivation surface of the stainless steel pipe is actually a very thin passivation film with a thickness of only 1-3 nanometers. Its local contamination and damage are the basic causes of stainless steel corrosion.

Protection of passivation film: During the manufacturing, storage, transportation and use of stainless steel pipes, especially during reprocessing, great attention must be paid to the protection of the surface passivation film to prevent collisions, contact with carbon steel strapping or slings, and forklift brackets. Ground storage, sewage soaking, etc.

Stainless steel pipes must be cleaned by special processes such as pickling and descaling, passivation or electropolishing before leaving the factory to remove oxide scale, iron ions and other foreign matter on the surface to obtain a passivated surface. The chemically inert and passivated surface naturally formed on the surface of clean stainless steel pipes in air or other oxygen-containing environments is the fundamental guarantee for the corrosion resistance of stainless steel pipes.