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Where is the corrosion resistance of stainless steel strip reflected
source：www.sikali.com.cn | Release time：2025年09月09日1、 Core mechanism: Self protection of surface passivation film
This is the fundamental reason for the corrosion resistance of stainless steel strips, and also the key difference from ordinary carbon steel:
Stainless steel strip contains chromium element (Cr, usually ≥ 10.5%), which rapidly undergoes oxidation reaction on the surface when in contact with air, water or oxygen, generating a very thin (thickness only 2-5nm), dense and continuous chromium oxide (Cr ? O ∝) passivation film.
This film has two major characteristics:
Isolation: tightly covering the surface of the stainless steel strip, acting like a "protective film" to block the contact between internal metal and external corrosive media (such as moisture, chloride ions, hydrogen ions), avoiding metal oxidation or dissolution;
Self repairing: If the passivation film is locally damaged due to mechanical friction, minor scratches, etc., the exposed fresh chromium will immediately react with oxygen in the environment, quickly regenerating a new passivation film at the damaged area, "repairing loopholes", and continuously maintaining corrosion resistance.
For example, the passivation film on the surface of 304 stainless steel strip used in daily life can resist moisture in the air and weakly acidic rainwater. Even if it comes into short-term contact with weak electrolytes such as soy sauce and vinegar, it will not rust as quickly as carbon steel.
2、 Tolerance scenario: "adaptability" for different types of corrosion
The corrosion resistance of stainless steel strip is not "certain", but it can effectively resist common types of corrosion in industrial and daily scenarios, including:
Atmospheric corrosion (most common)
Has excellent tolerance to dry, humid, or mildly polluted atmospheres such as urban air and inland environments. For example, stainless steel decorative strips and billboard frames used outdoors will only form slight "water spots" when exposed to air for a long time, and will not rust or peel off on a large scale like carbon steel.
Note: In high salt spray coastal environments, 316L stainless steel strips containing molybdenum should be selected to avoid point corrosion caused by chloride ions.
Corrosion of water and aqueous solutions
Almost non corrosive to clean fresh water (such as tap water and river water), can be used for stainless steel strips in water tank liners and pipes;
Has good tolerance to weakly alkaline solutions (such as dilute sodium hydroxide solution) and weakly acidic solutions (such as acetic acid and citric acid), suitable for lining belts in food processing and chemical storage tanks;
For strong chloride ion solutions such as seawater and chlorine containing wastewater, 316L or higher materials are required to avoid perforation caused by "pitting corrosion".
chemical medium corrosion
Differentiated tolerance for different chemical scenarios:
304 stainless steel strip can withstand dilute sulfuric acid and dilute hydrochloric acid (concentration<10%) at room temperature;
316L stainless steel strip can withstand higher concentrations of acids, alkalis, and organic solvents (such as ethanol and acetone), and is commonly used as a sealing strip for chemical pipelines and reagent packaging;
Special materials (such as Hastelloy strips) can withstand strong corrosive media (such as concentrated nitric acid, aqua regia), but the cost is relatively high and they belong to niche applications.
Corrosion in high/low temperature environments
At high temperatures (such as 300-600 ℃), 321 and 347 stainless steel strips containing titanium/niobium can prevent intergranular corrosion and are used as support strips for heating elements in boilers and ovens;
At low temperatures (such as -196 ℃ liquid nitrogen environment), the passivation film of 304 and 316L stainless steel strips can still remain stable, without the risk of low-temperature embrittlement or corrosion, and is suitable for sealing strips of low-temperature equipment.
3、 Process Assistance: The "Strengthening Effect" of Surface Treatment on Corrosion Resistance
In addition to the material itself, the subsequent surface treatment process of stainless steel strip will further enhance its corrosion resistance. Common methods include:
Polishing treatment: Through mechanical polishing (such as 8K mirror polishing) or chemical polishing, small surface depressions and scratches are reduced, the "attachment points" of corrosive media are lowered, and the passivation film is made more uniform, improving the ability to resist pollution and corrosion (such as food grade stainless steel conveyor belts and medical equipment belts).
Passivation treatment: Through chemical treatment with solutions such as nitric acid and chromic acid, the surface passivation film is artificially thickened to enhance its resistance to strong corrosive environments (such as passivation treatment before leaving the factory for chemical stainless steel strips).
Coating treatment: For special scenarios (such as strong acidic and alkaline environments), anti-corrosion coatings such as PTFE (polytetrafluoroethylene) can be applied to the surface of stainless steel strips to form a "dual protection", but it will increase costs and is suitable for extreme working conditions.
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