Does stainless steel lose its shine over time? Known for its excellent rust and corrosion resistance, stainless steel stands out among metals. However, improper maintenance and usage can dull its luster. Don’t worry! This article will explain why this happens and teach you how to avoid similar issues in the future.
What Is Stainless Steel?
Stainless steel is also called steel that is not easy to rust. Most stainless steels are both rust-proof and corrosion-resistant. Stainless steel contains very little iron, rich chromium (10-20%) and other elements. Stainless steel is often used in jewelry, manufacturing, medical equipment and kitchen utensils.
Here is a comparison of the common stainless steel compositions:
| Stainless steel grades | Carbon (C) | Chromium (Cr) | Nickel (Ni) | Manganese (Mn) | Molybdenum (Mo) | Silicon (Si) | Phosphorus (P) | Sulfur (S) | Other Elements |
| 304 | ≤ 0.08% | 18.0-20.0% | 8.0-10.5% | ≤ 2.00% | – | ≤ 1.00% | ≤ 0.045% | ≤ 0.030% | – |
| 316 | ≤ 0.08% | 16.0-18.0% | 10.0-14.0% | ≤ 2.00% | 2.0-3.0% | ≤ 1.00% | ≤ 0.045% | ≤ 0.030% | – |
| 303 | ≤ 0.15% | 17.0-19.0% | 8.0-10.0% | ≤ 2.00% | – | ≤ 1.00% | ≤ 0.20% | ≥ 0.15% | Sulfur is added to enhance machinability |
| 402 | ≤ 0.15% | 11.5-13.0% | – | ≤ 1.00% | – | ≤ 1.00% | ≤ 0.040% | ≤ 0.030% | Ferritic stainless steel |
| 403 | ≤ 0.15% | 11.5-13.0% | ≤ 0.50% | ≤ 1.00% | – | ≤ 1.00% | ≤ 0.040% | ≤ 0.030% | Adding trace amounts of aluminum to improve performance |
Will Stainless Steel Lose Its luster?
Yes, stainless steel will lose its luster. The composition of the stainless steel material and the environment in which it is used are the main factors that directly affect the luster .
Stainless steels that are less prone to tarnishing include austenitic, duplex and surgical grade stainless steels, which can effectively resist corrosion and oxidation due to their high content of chromium, nickel and molybdenum. However, martensitic, precipitation hardened and ferritic stainless steels are prone to tarnishing in high humidity, strong corrosion or long-term wear environments due to damage to the passivation film or oxidation reactions.
Next, we will analyze the gloss stability of common stainless steel types and their causes in detail :
Austenitic Stainless Steel
Austenitic stainless steel (such as 304, 316) has strong corrosion resistance and good gloss retention due to its high chromium and nickel content. Its crystal structure is face-centered cubic structure (FCC) , and its surface usually has a high reflectivity, so under normal use conditions, austenitic stainless steel has a strong ability to maintain gloss.
Martensitic Stainless Steel
Martensitic stainless steel (such as 420, 440C) has high hardness and wear resistance, and is often used to manufacture high-strength parts such as knives and bearings. However, the surface gloss of martensitic stainless steel is relatively low, and it is easy to lose its original gloss during long-term use due to factors such as wear and corrosion.
Ferritic Stainless Steel
Ferritic stainless steel (such as 430, 446) has excellent corrosion resistance due to its high proportion of chromium, and is often used in heat-resistant appliances, automobile exhaust systems, etc. Its surface gloss can usually remain stable under normal use conditions, but in humid, corrosive gas or high temperature environment, the surface is prone to oxidation and discoloration, thus affecting its gloss.
Duplex Stainless Steel
Duplex stainless steel (such as 2205, 2507) combines the characteristics of austenitic stainless steel and ferritic stainless steel, with excellent corrosion resistance and high strength. Duplex stainless steel is widely used in the fields of petroleum, chemical industry, etc., especially suitable for use in extreme environments. Due to its unique duplex structure, the gloss of duplex stainless steel is relatively stable in most environments.
Precipitation Hardening Stainless Steel
Precipitation hardening stainless steel (such as 17-4PH) has very high strength and hardness and is widely used in aerospace and high-strength applications. It has excellent corrosion resistance and gloss retention, but the surface may lose its gloss due to oxidation reaction under long-term high temperature or corrosive environment.
Surgical Grade Stainless Steel
Surgical grade stainless steel is used in medical devices and high-end jewelry. It contains 18%-20% chromium and 10%-14% nickel , which has excellent corrosion resistance and gloss stability. However, the gloss of surgical grade stainless steel may fade with long-term exposure to air and moisture.
Whether stainless steel loses its luster depends on the material it is made of, the environment it is in, and how it is used and maintained. Understanding these differences and taking appropriate protective measures when choosing the right stainless steel material will help extend its life and maintain its appearance.
Factors That Affect Stainless Steel Tarnishing
The surface of stainless steel sometimes loses its original luster. For example, in a humid environment , the passivation film of stainless steel will be destroyed, resulting in surface oxidation . Corrosive gases and chloride ions in seawater can accelerate corrosion. High temperature environment will accelerate oxidation reaction и reduce the luster.
By choosing corrosion-resistant stainless steel materials , avoiding harsh environments, and using the correct cleaning methods, the service life of stainless steel can be effectively extended and the luster can be maintained.The changes in material composition and principles involved behind each factor :
1. Humid Environment
When exposed to a humid environment for a long time, moisture forms a water film with dissolved oxygen in the air, which promotes the oxidation process. Stainless steel has a passive film, which protects the internal metal from oxidation.
However, oxygen molecules, carbon dioxide, chloride ions and other substances in the water film may damage the passivation film, causing oxidation reaction on its surface, resulting in loss of gloss. Especially in a high humidity environment, water accumulation is more likely to cause damage to the passivation film. In an environment with a relative humidity of more than 70%, the gloss of 304 stainless steel will drop significantly within 3-6 months .
2. Corrosive Gases
The corrosive gases such as sulfide and chloride contained in industrial waste gas pose a threat to the surface passivation film of stainless steel. These gases can react chemically with the chromium and iron on the surface of stainless steel to form soluble salts, which will weaken the stability of the surface passivation film and cause the stainless steel to lose its luster.
Especially in factories or chemical environments, the air is often filled with these corrosive gases. In an environment where the concentration of hydrogen sulfide gas is 100ppm, the gloss loss rate of the surface of 304 stainless steel is twice that of a normal environment.
3. Seawater Environment
Chloride ions in seawater are highly corrosive to stainless steel. The salt in seawater reacts with the chromium and nickel elements on the surface of stainless steel to form chlorides or chromium chloride, which in turn destroys the surface passivation film and causes the gloss to disappear quickly. After 3 months of exposure to seawater, the surface gloss loss of 316 stainless steel exceeds 30%.
4. Friction And Wear
The friction and collision between stainless steel and other objects will cause tiny scratches and wear on the surface. This physical damage will destroy the passivation film on the surface, causing the stainless steel to gradually lose its luster. For example, when using steel wool to clean, too rough objects will scratch the surface, leaving irreversible scratches and weakening the light reflection ability.
After being rubbed by rough objects, the surface glossiness of 304 stainless steel decreases by more than 50% when the roughness Ra value increases from 0.1µm to 0.6µm.
5. Chemical Exposure
When stainless steel comes into contact with strong acids, strong alkalis and other chemicals, the protective film on its surface will be quickly destroyed. Chemicals such as chloric acid and nitric acid will corrode the chromium oxide film on the surface of stainless steel, causing damage to the passivation film and local corrosion, which will then cause the gloss to be lost.
This phenomenon is particularly common in industrial cleaning and chemical experiments. After cleaning with strong acid, the surface corrosion rate of 304 stainless steel reaches 15%, and the glossiness decreases by more than 30%.
6. High Temperature Environment
The oxidation reaction in a high temperature environment will accelerate the oxidation and shedding of the passivation film on the surface of stainless steel. Especially when the temperature exceeds 500°C, the surface of stainless steel will undergo oxidation discoloration, resulting in a decrease in glossiness.
In kitchen equipment and other high-temperature operations , high temperature environments have a particularly significant impact on the surface of stainless steel. In an environment of 800°C, the surface of 304 stainless steel will form a 1μm oxide layer within 24 hours, and the glossiness will decrease by 35%.
7. Lack Of Cleanliness
The surface of stainless steel will gradually lose its luster if dust, dirt, oil stains and other impurities accumulate on it for a long time. Dirt not only covers the surface luster, but also accelerates the surface corrosion reaction, further affecting the appearance and function. Experiments show that the surface gloss of 304 stainless steel that has not been cleaned for a long time will decrease by about 20% within 3 months.
8. Improper Cleaning
Using inappropriate cleaning methods, such as steel wool, hard brushes or detergents containing abrasive ingredients , will scratch the surface of stainless steel and make it lose its luster. The correct cleaning method should choose a soft cloth and a mild detergent, and avoid using too rough tools.
How To Restore The Shine Of Stainless Steel ?
Once the stainless steel surface loses its luster, it can be effectively restored through surface cleaning, polishing and professional treatment methods.
Here are several effective restoration methods to help you restore the original luster of stainless steel.
1. Clean The Urface
Cleaning is the first step to restore the luster of stainless steel. By removing surface dirt, grease and oxide layers, you can not only restore some of the luster of stainless steel, but also prevent further damage to the surface.
- Use mild detergent : Mild detergent is the basis for maintaining the gloss of stainless steel surface. Strong acid, strong alkali or detergent containing abrasive will destroy the passivation film of stainless steel and cause surface corrosion. Specially designed stainless steel cleaner can effectively remove oil stains, dirt and scale, and restore the surface gloss. When using, first spray the detergent on a soft damp cloth, then gently wipe the stainless steel surface, avoiding excessive force to avoid scratching the surface.
- Vinegar and baking soda : Vinegar and baking soda are natural cleaners that can remove minor stains and restore the shine of stainless steel. Mix an appropriate amount of baking soda and vinegar into a paste, apply it to the stainless steel surface, and gently wipe with a damp cloth until the stain is removed. Baking soda has a mild scrubbing effect that can clean stubborn stains, while the acidity of vinegar helps remove oxides and mineral deposits.
- Lemon juice : Lemon juice is also a natural cleaner, and its acidity can remove oxides and scale on the surface of stainless steel. Simply squeeze lemon juice onto a damp cloth and gently wipe the stainless steel surface. After the stains are removed, rinse with clean water and wipe dry.
2. Polishing
After cleaning, the stainless steel surface usually still needs to be polished to restore its luster. Polishing can not only remove tiny scratches, but also form a protective film on the surface to prolong the retention time of the luster.
- Use stainless steel polish : There are special stainless steel polishes on the market. These products contain slightly abrasive particles that can remove tiny scratches on the surface of stainless steel and restore its gloss. When using, apply an appropriate amount of polish to the stainless steel surface and wipe it with a soft cloth or polishing wheel in a circular motion until the surface is as bright as new.
- Use car wax : High-quality car wax can not only provide a protective layer for the car, but also can be used to polish the surface of stainless steel. Apply an appropriate amount of car wax on the surface of stainless steel, wipe it evenly and polish it with a soft cloth. It can effectively restore the gloss and form a thin film on the surface to prevent stains and water stains from adhering.
3. Professional Processing
If the stainless steel surface is severely damaged, or cleaning and polishing cannot restore its luster, you can consider the following professional treatment methods.
- Ask professionals to handle it : For stainless steel that is deeply corroded or severely tarnished, you may need to rely on professional stainless steel cleaning and polishing companies. These companies have professional equipment and technology to perform deep cleaning, polishing and even re-passivation to restore the stainless steel to a near-original state.
- Repassivation : Passivation is a chemical treatment process that forms a dense oxide film on the surface of stainless steel, thereby enhancing its corrosion resistance and restoring its gloss. This method is suitable for surfaces that have been oxidized or corroded for a long time and requires professional equipment and technical operation.
Вопросы и ответы
Will Stainless Steel Lose Its Luster In Water?
Stainless steel usually does not lose its luster in water. It contains alloy elements such as chromium, which can form a thin oxide film on the surface. This oxide film can protect the internal metal and prevent water and oxygen from entering, thereby preventing rust and tarnishing. However, if the water contains more chloride ions (such as seawater) , long-term contact will cause the stainless steel to gradually lose its luster and even rust spots.
Will Stainless Steel Lose Its Luster After Cleaning?
Stainless steel does not necessarily lose its gloss after cleaning. If the appropriate cleaning method and mild detergent are used, stainless steel can maintain its gloss after cleaning. For example, gently wiping with a soft cloth dipped in a mild detergent solution, then rinsing with clean water and drying will generally not have a significant impact on the gloss. However, if rough cleaning tools such as steel wool or highly corrosive detergents are used, the surface of the stainless steel may be scratched or the protective film on the surface may be damaged, resulting in a decrease in gloss.
Will Stainless Steel Rings Tarnish?
Stainless steel rings usually maintain their luster for a long time because the chromium element in the alloy forms a dense chromium oxide protective film on the surface. This film can effectively isolate air and moisture, provide excellent anti-oxidation and anti-corrosion properties, and keep the ring’s brightness stable during daily wear.
However, if the ring is frequently exposed to chloride-containing environments (such as swimming pool water, sea water or chlorine-containing cleaning agents), chloride ions may attack the oxide film, causing its protective effect to weaken, and the ring’s surface gloss may decrease over time. To maintain the long-term brightness of the ring, it is recommended to avoid contact with corrosive chemicals and clean and maintain the surface regularly.
Will 18k Gold Plated Stainless Steel Tarnish?
18K gold-plated stainless steel may lose its luster due to daily wear and tear. Since the gold-plated layer is thin, friction when in contact with other objects can easily cause the plating to wear away, causing the luster to fade. In addition, the chemical components in perfume, cosmetics and sweat can also react with the gold-plated layer, causing discoloration and loss of luster. At the same time, the gold-plated layer is also easily corroded in a humid environment for a long time, thus affecting the durability of the appearance.
Will Stainless Steel lose Its Luster?
Plated stainless steel tends to lose its luster during use. Since the coating is thin, if the adhesion is not strong, the coating may peel off, resulting in a decrease in gloss. Daily friction can also cause the coating to gradually become thinner or even disappear, losing its original brightness. In addition, in high temperature, high humidity or polluted environments, the coating may oxidize or corrode, further affecting its gloss.
Заключение
Stainless steel may lose its luster under corrosion or excessive friction, but with its corrosion resistance and wear resistance, it has become an important material innovation in the history of human industry. It is this durable property that makes stainless steel play a key role in many fields, promotes the development of modern industry, and lays the foundation for long-lasting and stable product design.