Understanding Stainless Steel’s Corrosion-Resistant Properties

Whether for the consumer market or industrial use, one of the most popular reasons for choosing stainless steel is its corrosion-resistant properties.

However, the exact resistance levels and weaknesses of a stainless product, sheet or bar will depend on both it’s metallurgic composition and how it was made.

This guide covers the various types of corrosion to be wary of while working with stainless steel and other concerns that might impact either the visual appearance or performance of popular stainless steel grades.

But before we dig into the details, let's take a look at what makes stainless so resistant in the first place…

How Does Stainless Steel Resist Corrosion?

While various stainless steel grades might differ in their metallurgic composition and alloying or manufacturing processes, one trait they all share is a passivation layer.

This layer of chromium oxide forms when the surface of the metal is exposed to oxygen.

The layer is too thin to observe directly and under most circumstances remains clear. This allows the finished texture of a stainless steel product to show through and provides a variety of appearance options from high gloss to matte.

Impervious to water, the passivation layer is self-generating and serves to protect the metal. While it might discolor under extreme temperatures, it’s still working.

However, stainless steel is not invincible. It’s still susceptible to corrosion under the right situations.

Stainless Steel and Chemical Compounds: What to Consider

One of the most common scenarios in which stainless steel corrodes is through sustained contact with liquids or chemicals.

Known as general corrosion, this type is typically uniform across the surface of the steel. Fortunately, most stainless steels respond in a predictable manner to a range of chemicals.

If you’re planning to use stainless steel, consider exposure to the following to gauge general corrosion risks.

Acids

Stainless steel is generally resistant to acidic corrosion. However, exact resistance levels will depend on the steel in use, concentration, and types of acid, and environmental temperature.

For example:

• Grades 316 and 317 offer resistance to phosphoric acid at most concentrations and sulfuric acid at concentrations below 10 percent.
• Grade 904 offers resistance to high concentrations of sulfuric acid.
• Types 304L and 430 offer resistance to nitric acid.

Hydrochloric acid is an exception to the general acid resistance of stainless steel and should be avoided.

Bases

Stainless steel offers strong resistance to weak bases in both high concentrations and high-temperature environments. However, stronger bases will cause cracking or etching corrosion. Particular care must be taken with chloride solutions such as sodium hypochlorite.

Organics

Resistance to organics differs. In general, 300-series steels perform best with these solutions. However, exact recommendations vary based on environmental factors such as temperature and oxygen availability.

If you’re planning to use stainless steel to store organics, consulting a professional, such as Unified Alloys, can help to both highlight concerns and identify options to create a safe, long-lasting stainless steel solution.

Specialized Types of Stainless Steel Corrosion and Damage

Apart from general corrosion, stainless steel corrosion can take on several specialized forms.

Fortunately, there are ways to address most forms or avoid them entirely. The following are common forms of specialized corrosion.

1. Galling

This corrosion occurs when stainless steel parts are forced together. Commonly seen with nuts, bolts, and other fasteners, corrosion isn’t visible until the parts are separated or disassembled.

The process uses repeated passes to adjust the dimensions of the steel slowly. In most cases, this will involve rolling through multiple mills over time to achieve the desired thickness.

2. Galvanic

Also known as bimetallic corrosion, this corrosion occurs when stainless steel is used with other metals in a moist environment. Rain, condensation or other moisture sources can act as an electrolyte in the presence of an electrical current causing one metal to corrode at an accelerated rate.

Exact characteristics of galvanic corrosion vary based on metals used, temperatures, areas of contact and other factors. For more information on the topic, consulting the British Standards Institution’s PD 6484 is recommended.

3. Pitting

This corrosion is typically a result of exposure to chemicals in the environment or poor aeration. It is also more common in steels with unwanted inclusions or manufacturing defects. For example, Manganese (II) Sulfide often initiates pitting.

Adequate oxygen availability can help to reduce the rate of pitting corrosion or halt it entirely depending on the cause. Steels with molybdenum also have an increased ability to both resist pitting and slow its progress. Other considerations include pH, chloride concentration and temperature of the environment in which the steel is used.

4. Crevice Corrosion

This corrosion occurs when a crevice between the stainless steel and another material allows chlorides to concentrate or prevents proper oxygen levels to regenerate the steel’s oxide layer. While typically found near or within the gap between two metals, crevice corrosion can also occur between metallic and non-metallic surfaces.

Welding, ensuring proper drainage and using proper gaskets can also help to prevent crevice corrosion as these all help to decrease access to crevices or eliminate them altogether.

5. Weld Decay

Also known as intergranular corrosion, this corrosion results from heating stainless steel to a specific temperature range—often between 550C and 850C. This causes chromium to precipitate from the stainless steel and reduces the ability for the passivation layer to regenerate.

Using low carbon steels—such as 304L and 316L—when welding can help to reduce the impact of weld decay. Additives such as titanium or niobium can further stabilize the steel and reduce precipitation while welding. In all cases, using a post-weld heat treatment is recommended to minimize corrosion.

Final Thoughts

Keeping stainless steel looking and performing great is all about protecting the chromium layer that gives it stainless properties.

This also improves safety by ensuring that your stainless steel structures, containers and equipment stay structurally sound for as long as possible.

By considering the environment in which your stainless steel is used—and matching the grade to your intended application—you can optimize corrosion resistance and ensure long-lasting results for your investment.

Though this guide offers a good starting point on different corrosion types and prevention measures, consulting with a professional is always recommended to ensure an ideal product fit and safety.

Unified Alloys offers more than 40 years of expertise serving some of the biggest industries in Canada and North America. Have a question about stainless steel corrosion or applications? Call us and we’d be happy to discuss your needs and find the perfect solution.

Introduction

More manufacturing industries relying on stainless steel to construct durable and reliable machining components are making stainless steel rods a popular choice.

Stainless steel rods are becoming increasingly popular in many manufacturing industries, such as construction, automotive, and aerospace. This is due to the high durability, strength, and corrosion resistance properties of stainless steel rods.

However, there are different types of stainless steel rods available in various sizes and grades. How do you decide which one is right for your application? Which grade and type of stainless steel rods to choose? You will get answers to these questions and more.

This blog discusses everything you need to know about stainless steel rods, including what they are, where to use them, the benefits they offer, and the different types and grades of stainless steel available.

Keep reading to learn more, or jump ahead to the topic you’re looking for:

What Are Stainless Steel Rods?

Stainless steel rods, also known as stainless steel bars, are a type of stainless steel product most commonly used in food, construction, and manufacturing industries. These SS rods are available in various sizes and shapes, like round, square, and hexagonal. 

Stainless steel rods are highly valued due to their beneficial properties like greater performance in high-temperature conditions, superior resistance from corrosive chemicals and other abrasive fluids, high durability, and strength for long service life, and a high level of hygiene, which makes them suitable for food industries. 

Different Types Of Stainless Steel Rods

Different Stainless Steel Rods Grades 

Being a leading Stainless Steel Rod manufacturer in India, we offer SS rods in a variety of grades. There are over 150 stainless steel grades available, but not all are suitable for every industrial purpose. 

Below are some of the widely used SS rod grades with their features and applications.

➤ 303 Stainless Steel

Features: 

• Durability
• Heat resistance  
• Corrosion resistance 

Applications:

• Commonly used for gears, shafts, aircraft fittings, and commercial applications such as food handling and processing equipment, screws, machinery parts, utensils, and exhaust manifolds. 

➤ 304 Stainless Steel

Features: 

• Easy to clean
• Strong and durable
• Excellent corrosion resistance

Applications:

• Widely used in various applications such as manufacturing food handling and processing equipment, machinery, screws, exhaust manifolds, etc.

➤ 309 Stainless Steel

Features: 

• Resistant to corrosion
• Heat and oxidation resistance 
• High tensile strength 

Applications:

• Due to excellent resistance to heat, creep deformation, and environmental attack, it is used for manufacturing heating elements. Aircraft and jet engine parts.

➤ 15-5ph Stainless Steel 

Features: 

• High strength and hardness 
• Excellent corrosion resistance
• Good mechanical properties 

Applications:

• Mainly used for constructing Aerospace structural components, valves, gears and shafts, oil and gas components, and nuclear reactor components.

➤ 316 Stainless Steel 

Features: 

• Excellent weldability and toughness 
• Great machinability 
• Resistance to corrosion from chloride and other acids
• Contains high molybdenum content, suitable for marine applications

Applications:

• Primarily used in the construction of exhaust manifolds, furnace parts, heat exchangers, jet engine parts, valve and pump parts, chemical processing equipment, pharmaceutical and photographic equipment, tanks, and evaporators.

➤ 17-4ph Stainless Steel 

Features: 

• Superior toughness and strength in high temperatures
• Corrosion resistance 
• Cost-effective

Applications:

• Preferred choice for chemical, dairy, food, paper, and petroleum applications.

➤ 416 Stainless Steel

Features: 

• Corrosion and wear resistance
• High tensile strength
• Good ductility and machinability

Applications:

• Used for manufacturing various machining components like electrical motors, nuts, and bolts.

Advantages Of SS Rods 

It’s probably clear now that stainless steel rods are pretty great for various applications. Still, this deserves to be broken down in detail. The benefits of stainless steel rods can make up a lengthy list; however, here are the main advantages of stainless steel rods: 

1. High Strength: 

Has high strength and durability that offers the capability to withstand heavy loads and stress without breaking. 

2. Corrosion Resistance: 

Highly resistant to corrosion due to the chromium content in it. Ideal for usage in harsh environments where higher corrosion resistance and strength are required.

3. Hygiene:

SS rods are easy to clean and have various hygiene properties, making them a great choice for hospitals and the food industry when cleanliness and protection from harmful bacteria are essential.

4. Aesthetic Appearance: 

Provides a sleek and high-quality appearance; hence, popular for decorative applications and heavy-duty industrial use.

5. Resistance To Heat:

Due to high heat resistance, it can maintain its strength and shape at the highest temperatures 

6. Long Service Life: 

SS rods are highly durable, require minimal maintenance, and reduce frequent replacements, which ultimately increase the lifespan of the product.

7. Recyclability:

Stainless steel rods are easily recyclable without losing their quality and performance. This helps in conserving natural resources and reducing energy consumption, making them a sustainable choice for industries.

Stainless Steel Rods Applications

Stainless steel rods are the right choice for the following applications:

• Automobile industries
• Heavy engineering
• Textile industries
• Electric motors
• Industrial pumps
• Agriculture Section
• Oil & petroleum
• Aerospace
• Architectural applications
• Marine applications
• Ocean bottoms and oceanside structures
• Defense
• Medical tools 
• Valve Manufacturing
• Bearing manufacturing and many more.

How To Select The Right SS Rods? 

If you have decided that a stainless steel rod is the best choice for your application, follow the tips below to comprehend which one is right for you.

Tip 1: Determine the type of application you need SS rods for. This will allow you to identify the size and type of stainless steel. 

Tip 2: Choose the right material for stainless steel rods. After considering your application requirements, select the SS rod material that offers the required strength, corrosion resistance, and other characteristics required for your particular needs.

Tip 3: Take a closer look at the surface finish of SS rods. For example, if you need stainless steel bars for hygiene requirements, go for smooth and polished finishes for suitable protection from corrosion and wear.

Final thoughts

This guide contains everything you need to know about stainless steel rods. After reading this, you are equipped with the proper knowledge about stainless steel bars, their types, grades, characteristics, and applications. 

If you are interested in purchasing premium quality stainless steel rods for your application, we recommend you share your requirements with Vishwa Stainless Pvt. Ltd.

Vishwa Stainless Pvt. Ltd. is one of the premier SS Rod manufacturers and suppliers in India. We specialize in providing exceptional quality stainless steel products in various grades and sizes. 

Please feel free to contact us for product requirements at sales@vishwastainless.com, and we will get back to you soon.

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