How chlorides affect corrosion in stainless steel storage tanks
Chlorides are a common cause of corrosion in stainless steel storage tanks and pressure vessels. Although stainless steel 304 and acid-proof 316/316L have good corrosion resistance, chlorides can affect the protective surface layer of the material and lead to, for example, pitting and crevice corrosion.
The risk of corrosion attack increases at higher chloride levels, especially in combination with elevated temperature or stagnant liquid.
In areas such as food production, the chemical industry and water treatment, material selection and surface finish are therefore important factors. Acid-resistant 316/316L, which contains molybdenum, is often used in environments with higher requirements for resistance to chlorides.
Process Surplus offers tanks in stainless steel 304 and acid-proof 316/316L in various designs. Available information on materials and construction can be used as a basis for selecting a tank for applications where chlorides are present.
Function and structure
Stainless steel storage tanks are designed to store liquids without contamination or material degradation. Chlorides do not affect the mechanical structure of the tank but can degrade the passive surface that protects the steel.
- Stainless steel tank body
- Welded joints and seams
- Inspection hatches and inlets and outlets
- Agitators or processing equipment if needed
- Insulation in temperature-sensitive processes
Materials and corrosion mechanisms
Stainless steel 304
Stainless steel 304 has good corrosion resistance but is susceptible to chloride-related pitting corrosion, especially in salt water or with stagnant liquids. Welded joints and scratched surfaces are particularly vulnerable.
Acid resistant 316 and acid resistant 316L
316 and 316L contain molybdenum which increases resistance to chlorides. These materials are used in environments where chloride levels can be high, for example in water treatment or chemical handling. Spot and crevice corrosion is much less likely.
Pressurized and atmospheric solutions
Chlorides can affect both pressurized and atmospheric storage tanks. In pressurized tanks, corrosion risks are amplified at welded joints and tight angles. Atmospheric tanks can be affected by chloride-containing air or condensation collecting on the inside.
Applications in industry
- Food industry – salt and acids can increase corrosion
- Chemical industry – handling of chloride-containing solutions
- Pharmaceutical production – CIP cleaning with chlorides
- Water treatment – salt and disinfectants
Technical options and preventive measures
To reduce corrosion from chloride exposure, several measures can be taken:
- Using 316L or duplex material
- Polishing the tank surface to strengthen the passive film
- Installing CIP systems for regular cleaning
- Avoiding stagnation and high temperature
- Monitor chloride levels in the liquid
Volumes and capacity
Process surplus offers tanks in various sizes, from about 100 liters up to 250,000 liters, in several materials and designs.
The choice of material is mainly influenced by the chemical properties of the liquid, such as chloride content, and the requirements of the process in question, rather than just the volume of the tank.
For larger volumes and more demanding applications, acid-proof 316/316L is often used, which has higher resistance to corrosion in environments where chlorides are present.
The benefits of choosing the right materials
- Reduced risk of pitting and crevice corrosion
- Longer life and reduced maintenance
- Stable hygiene and process continuity
- Possibility to use aggressive cleaning agents without damage
New and used tanks in stock
PProcessöverskott offers both new and used storage tanks in stainless steel 304 and acid-proof 316/316L in various designs.
Tanks are available in several sizes and materials, allowing solutions to be chosen to suit applications where, for example, chlorides are present.
Many tanks are available for quick delivery depending on stock status and are used in different types of industrial processes.
Choosing the right solution
In high chloride environments, acid resistant 316/316L is often used due to its better resistance to corrosion.
For less demanding applications and fluids with lower corrosive impact, 304/304L stainless steel may be an option, depending on process conditions.
Factors such as surface treatment, weld design and periodic inspection have an impact on how the material is affected over time and are important to consider when operating in corrosive environments.
Executive summary
Chlorides can pose a risk of corrosion in stainless steel storage tanks, especially at higher concentrations and under harsh operating conditions.
Stainless steel 304 is often used in milder environments, while acid-resistant 316/316L is common in applications with higher chemical loads, for example in the presence of chlorides.
The choice of materials and workmanship, together with factors such as surface finish and maintenance, have an impact on how the tank is affected over time.
Process Surplus offers tanks in stainless steel 304 and acid-proof 316/316L in various designs. Available information on materials and construction can be used as a basis for selecting a tank for different types of industrial applications.
Frequently asked questions about how chlorides affect corrosion in stainless steel storage tanks
How do chlorides affect corrosion in stainless steel storage tanks?
Chlorides can affect the protective oxide layer of stainless steel and lead to corrosion forms such as pitting and crevice corrosion.
The risk of such attacks increases at higher chloride levels, elevated temperatures, for example above about 40 °C, and when the liquid is stagnant.
Acid-resistant 316/316L, which contains molybdenum, has a higher resistance to these types of corrosion and is often used in more demanding environments.
This is particularly relevant in applications such as the chemical industry, pharmaceutical production and water treatment where the choice of material is of great importance.
Is 304 stainless steel safe for chloride exposure?
Stainless steel 304 is often used in milder environments, but can be affected by liquids with chloride content, such as salt water or certain cleaning chemicals.
Welded joints and surfaces with damage or scratches are particularly vulnerable to corrosion.
At higher chloride levels, acid-resistant 316/316L is often used, which has better resistance to this type of impact depending on the application and operating conditions.
How to prevent chloride-related corrosion?
Preventive measures against corrosion in tanks can involve several different factors depending on the application and operating conditions.
Common measures include:
- Choice of material, such as acid-proof 316/316L or in some cases duplex material for more demanding environments
- Customized surface finishes, such as polished surfaces, to reduce the risk of infestation
- Avoidance of stagnant liquid where stagnation can increase the risk of corrosion
- Control of temperature and chloride levels in the process
- Regular cleaning, for example via CIP systems depending on the application
The measures to be taken will vary depending on the characteristics of the fluid, its design and operating conditions.
Does tank size affect corrosion risk?
Size does not affect the corrosion mechanism itself, but larger tanks may have areas of low liquid circulation that increase the risk of crevice corrosion. Material selection and design are crucial for protection against chlorides.
Which industries are most affected by chloride corrosion?
Applications in food production, chemical industry, pharmaceutical production and water treatment can be more vulnerable to corrosion effects, especially in the presence of chloride-containing liquids.
In such environments, acid-proof 316/316L is often used due to its higher resistance to corrosion compared to stainless steel 304.
The choice of material has an impact on how the tank is affected over time and is an important factor to consider in processes with hygiene and durability requirements.