Will Stainless Steel Rust and How Can You Solve It?

Stainless steel is not completely rustproof. In this article, we will explain to you when stainless steel will rust, what types of corrosion it may suffer, effective measures to prevent and solve rust, and provide some stainless steel models with high corrosion resistance. By reading this article, you can understand the durability and performance of stainless steel in various application scenarios.

Does Stainless Steel Rust?

Yes. The corrosion resistance of stainless steel depends on the chromium oxide passivation layer on the surface. However, in high-salt, humid, or high-temperature environments, this protective film may be damaged, causing rust. The rusting speed is affected by the environment and the type of stainless steel, especially the presence of chloride ions, which accelerates corrosion.

Why Doesn’t Stainless Steel Rust?

Stainless steel resists rust because it contains at least 10.5% chromium, which forms a thin, protective layer of chromium oxide on the surface. This layer prevents oxygen and moisture from reaching the steel, stopping rust from forming. Even if the surface is scratched, the chromium oxide quickly reforms, maintaining corrosion resistance.

Why Does Stainless Steel Rust?

When the passive layer is destroyed and the iron is exposed, it reacts with water and oxygen in the air to form iron oxide (rust). The causes of passive layer destruction are various, including but not limited to mechanical wear, chemical corrosion, and contamination by iron particles.

Mechanical Abrasion

Scratches and physical damage to the stainless steel surface can break the protective chromium oxide layer. This can occur during fabrication, installation, or regular use. Tools like steel wool, wire brushes, or any abrasive materials can damage the passive layer, exposing the underlying metal to the environment.

Chemical Exposure

Certain chemicals can react with stainless steel, compromising its protective layer. For example, acids and alkaline solutions, particularly those containing chlorides, can lead to localized corrosion. Chloride-containing cleaners commonly found in homes and industries are particularly dangerous, as they can damage stainless steel by triggering localized corrosion, such as pitting and crevice corrosion.

Environmental Conditions

Harsh environmental conditions, such as long-term high humidity, salty air, and extreme temperature changes, challenge the chromium oxide layer on the surface of stainless steel and reduce its protective effectiveness. Stainless steel structures near coastal areas or in industrial environments are especially susceptible due to the presence of salt and pollutants in the air.

Contamination with Iron Particles

During the production process, stainless steel may be accidentally contaminated with iron particles from tools, machinery, or other steel products. These iron particles will oxidize and rust on their own, which will trigger a chain reaction of corrosion on the surface of the stainless steel.  It’s crucial to use dedicated tools and clean workspaces to prevent cross-contamination.

Improper Maintenance

Failure to properly clean and maintain stainless steel can lead to the accumulation of dirt, grease, and other contaminants. These substances can trap moisture and promote rust formation. Taking proper cleaning measures to maintain the integrity of the passivation layer on the surface of stainless steel is an important part of ensuring its long-term durability.

Heat Treatment and Welding

Heat treatment and welding can cause changes in the microstructure of stainless steel, leading to the formation of chromium carbides at the grain boundaries. This process, known as sensitization, depletes the chromium content in these areas, making them more susceptible to intergranular corrosion.

The Corrosion Process

Initiation: The corrosion process begins when the protective chromium oxide layer is compromised. 

Oxidation: When iron is exposed to oxygen and moisture, it undergoes an oxidation reaction, forming iron oxide (rust). Chloride ions are present to function as a catalyst, making the oxidation process faster.

Propagation: Once rust begins to form, it can spread rapidly, particularly in the presence of moisture and oxygen. The rust itself can trap moisture, further accelerating the corrosion process and causing mental damage.

Structural Degradation: Over time, the accumulation of rust weakens the metal, leading to structural degradation. This can compromise the integrity of stainless steel components, causing them to fail or require costly repairs and replacements.

Types of Corrosion of Stainless Steels

Pitting Corrosion

Pitting is a localized, severe corrosion of metals that forms small holes or pits commonly found in chloride-containing environments such as seawater or de-icing salts. It is dangerous because it is difficult to detect and can penetrate deep into the metal, becoming the source of other corrosion and mechanical failures.

Crevice Corrosion

Crevice corrosion takes place in confined spaces, such as gaps between parts, under gaskets, or in metal crevices. The low-oxygen environment aggravates corrosion, and the formation of a protective chromium oxide layer is blocked, ultimately leading to local corrosion and structural weakening.

Bimetallic (Galvanic) Corrosion

When stainless steel comes into contact with other metals in an electrolyte, bimetallic corrosion occurs; that is, the potential difference drives the anode metal to accelerate corrosion, which is common in metal combinations in humid environments.

Stress Corrosion Cracking (SCC)

Stress corrosion cracking (SCC) is the phenomenon of crack extension under the combined effect of corrosion and stress. It is common when stainless steel is subjected to tensile stress and specific corrosive media (such as chloride ions), which may lead to catastrophic failure without warning.

General (Uniform) Corrosion 

Uniform corrosion results in the even loss of material over the entire surface. It is predictable and often manageable with protective coatings or corrosion inhibitors. This type of corrosion is less dangerous than localized forms because it is easier to detect and control. General corrosion typically occurs in environments where the entire surface is exposed to a corrosive medium, leading to a consistent rate of material loss.

Intergranular Attack and Weld Decay

Intergranular corrosion occurs at the grain boundaries of stainless steel, often caused by the precipitation of chromium carbides during welding, resulting in a decrease in chromium content at the grain boundaries and a decrease in corrosion resistance. Weld corrosion is a special form of intergranular corrosion that affects the welding area and creates potential weaknesses in the structure.

How to Prevent Stainless Steel from Rusting?

Preventing rust on stainless steel involves several strategies that can be implemented during the design, fabrication, and maintenance stages:

1. Design

Proper design can minimize water penetration and reduce potential damage. Ensure good drainage and air circulation to avoid crevices and moisture accumulation. Designs that avoid sharp corners, crevices, and areas where water can accumulate will help prevent corrosion. Including drainage holes and ensuring that surfaces are easily cleanable can also reduce the risk of corrosion. To prevent stainless steel corrosion, our factory optimizes the structure when designing to reduce moisture retention.

2. Fabrication

During the manufacturing process, ensure that stainless steel is completely isolated from carbon steel to prevent any form of direct contact, use stainless steel-specific tools and equipment, and maintain a highly clean working environment to prevent carbon steel particles from contaminating the stainless steel surface and affecting its corrosion resistance.

3. Maintenance

Regular maintenance of stainless steel is essential. Cleaning is carried out using non-abrasive tools and mild detergents, avoiding the use of hard materials that may damage the surface. Pay special attention to choosing chlorine-free or low-chlorine detergents to reduce the risk of pitting. Regularly inspecting the surface of stainless steel to detect and treat any signs of corrosion in a timely manner can effectively extend its service life.

4. Water Treatment

Use treated water to reduce mineral deposits and corrosion risk. Softened water helps prevent deposits that can break down the passive layer. Water treatment systems can remove harmful minerals and impurities, ensuring that the stainless steel remains protected. In areas with hard water, regular maintenance and cleaning are particularly important to prevent the build-up of deposits.

5. Protective Coatings

To further enhance the corrosion resistance and aesthetics of stainless steel, high-quality protective coatings such as polyurethane and epoxy resin can be applied. These coatings can effectively block corrosive elements in the environment and protect the stainless steel substrate from damage. Also, periodically check the integrity and adhesion of the coating and, if necessary, paint or recoat it to ensure its continued effectiveness.

As a manufacturer specializing in stainless steel products, our factory has implemented careful measures in the production process. We strictly classify, operate with special tools, and use advanced water treatment technology to ensure pure production. Regularly maintain the coating to protect the durable quality.

Choose us, you choose high-quality, easy-to-maintain, and durable stainless steel products!

Stainless Steel Grades with Better Corrosion Resistance

Choosing the right Grade of stainless steel is crucial, as not all stainless steel grades are created equal in terms of corrosion resistance. Choose the right grade for your specific application:

• Grade 304 stainless steel, a type of stainless steel that is widely used in the market, has excellent corrosion resistance under various environmental conditions due to its ratio of 18% Cr to 8% Ni.

• Grade 316: Contains 16% Cr, 10% Ni, and 2-3% Mo. The addition of molybdenum improves resistance to chlorides and other corrosive substances, making it suitable for marine and industrial applications.

• Grade 317: Similar to 316 but with higher Mo content for even greater resistance to chemical attack.

• Grade 321: Contains Ti, which stabilizes the structure against chromium carbide formation, making it ideal for high-temperature environments.

• 2205 Duplex: Contains 22% Cr, 5% Ni, and 3% Mo, which further enhances its protection against stress corrosion cracking, pitting, and even crevice corrosion.

• 2507 Super Duplex: Contains 25%Cr, 7%Ni, and 4%Mo, providing excellent corrosion resistance, especially in highly corrosive environments such as offshore and chemical processing.

• Grade 439: It not only performs better in stress corrosion cracking resistance but also significantly improves weldability and broadens its application areas.

• Grade 17-4 PH: Contains 17% Cr, 4% Ni, and Cu, offering a combination of high strength, hardness, and corrosion resistance. Used in aerospace, chemical, and petrochemical industries.

How to Remove Rust from Stainless Steel?

When you encounter rust on stainless steel, you can also use a special rust remover to remove the rust.

DIY——Lemon, Lime, and Salt

Mix lemon/lime juice and salt to make a scrubbing paste. The citric acid breaks down the rust, and the salt helps abrasive removal. It works well on small rust spots and is suitable for daily maintenance.

Store-Bought Rust Removers

For severe rust, using a commercially available professional rust remover is an effective method. These products can dissolve stubborn rust and restore the shine of stainless steel. When using, follow the manufacturer’s instructions carefully to ensure effectiveness and safety. Provide ventilation when operating to protect your personal health.

Industrial Methods

Large or severely rusted items can be treated with sandblasting or chemical soaking. Sandblasting uses high-speed abrasives to remove rust, while chemical soaking immerses the item in a rust-dissolving solution. These methods are often used in industrial environments.

You may also want to know:

Will Stainless Steel Rust Outdoors?

Generally no. Stainless steel will resist rusting outdoors due to its protective chromium oxide layer, but some grades of stainless steel may still corrode over time in harsh environments (such as salty coastal areas).

Will Stainless Steel Rust in Water?

Possibly. Stainless steel will not typically rust in fresh water due to the chromium it contains. However, prolonged exposure to water (especially non-high-grade stainless steels) can cause surface corrosion.

Will Stainless Steel Rust in Salt Water?

Yes, stainless steel will rust over time in salt water, especially lower grades such as 304. For better corrosion resistance, 316 stainless steel, which contains molybdenum, is recommended.

Will Surgical Steel Rust?

Generally no. Surgical steel is a type of stainless steel with high corrosion resistance that will typically not rust even in body fluids. It is specifically designed to withstand harsh environments and is suitable for use in implants and surgical tools.

Get Satisfactory Stainless Steel！

Now you know the reasons why stainless steel rusts, the types of rust, and the effective measures to prevent & solve rust. If you want to buy corrosion-resistant stainless steel or are confused about the grade selection, please contact our metal experts. As a professional supplier of special steel, we are very happy to help you choose the most suitable product!