Corrosion presents a major and expensive challenge for various industries, particularly in chemical plants where the regular handling of harsh chemicals is commonplace. The reliable performance and dependability of equipment, such as valves, are vital for maintaining safe and effective operations in these demanding environments.
This article discusses the negative impacts of corrosion and highlights the heightened susceptibility of valves in the chemical industry. However, before exploring the significance of corrosion resistant valves in chemical plants, it is essential to understand the underlying causes of corrosion.
What Causes Valve Corrosion?
Corrosion originates from chemical reactions that affect the surfaces of metal. The valve, being exposed to particular environmental conditions such as harsh chemicals or water evaporation from leaks or spills, is susceptible to corrosion, leading to gradual cracking of the metal. The corrosion of the valve stem can be attributed to various factors, these are the 4 main factors:
1. Fluid Composition
The presence of certain gases, such as CO2 (carbon dioxide) and H2S (hydrogen sulfide), in fluid compositions can lead to corrosion problems in various industries.
However, when these gases come into contact with liquid water, they dissolve and form acidic compounds that have corrosive properties. This can pose a significant corrosion risk to equipment and infrastructure in the industry.
2. Microbially Induced Corrosion
This form of corrosion occurs when valves are exposed to sulfate-reducing bacteria (]SRB) and organic sediments, particularly in scenarios such as buried pipelines or areas with significant marine growth. The SRB feed on organic acids, oxidizing them and generating sulfide ions (S2- and HS–). These sulfide ions then react with the valve steel, resulting in the formation of an iron sulfide film.
3. Stress Corrosion Cracking (SCC)
This phenomenon occurs as a result of specific corrosive environments, certain alloys, and tensile stress. Examples when the valve is constantly exposed to the corrosive fluid, and it operates under high pressure and temperature conditions due to the nature of the process. The combination of stress, corrosion, and the presence of certain environmental factors can lead to SCC in this valve.
Types of Valve Corrosion in the Chemical Industry
or valve corrosion, each of which plays a significant role in the deterioration of valves. These factors include:
1. Galvanic Corrosion
When dissimilar metals contact a corrosive liquid and electrolyte, a primary cell forms, generating a current that accelerates the corrosion of the anode. Corrosion typically concentrates near the contact point. Metal plating techniques can be employed to mitigate this type of erosion.
2. High-Temperature Corrosion
To assess high-temperature oxidation effects, we analyze metal composition, atmosphere, temperature, and exposure duration. Light metals tend to develop non-protective oxide layers that gradually peel off as the weight of the oxide exceeds that of the underlying metal. Moreover, high-temperature corrosion can manifest in different forms like sulfidation and carburization.
3. Crevice Corrosion
This phenomenon occurs along the seam, impeding oxygen diffusion and creating areas with different oxygen levels, resulting in varying solution concentrations. Defects in joints or welding joints, specifically narrow gaps measuring 0.025 to 0.1mm, allow electrolyte solutions to penetrate. This forms a short-circuit primary cell between the metal inside the gap and the metal outside, leading to intense localized corrosion within the gap.
4. Pitting Corrosion
Local corrosion or pitting corrosion occurs when the protective film is damaged or the corrosion product layer decomposes. The rupture of the film creates an anode, while the intact film or corrosion products act as a cathode, forming a closed circuit in the presence of chloride ions. This makes certain stainless steels prone to pitting corrosion. Irregularities or rough areas on the metal surface, lacking uniformity, contribute to the occurrence of corrosion.
5. Intergranular Corrosion
Intergranular corrosion is caused by various factors, resulting in damage along the metal’s grain boundaries and deterioration of mechanical properties. Austenitic stainless steel is particularly susceptible to this type of corrosion within the temperature range of 800 to 1500°F (427-816°C), unless appropriate heat treatment or contact sensitization methods are applied.
To mitigate intergranular corrosion, options include pre-annealing and quenching the stainless steel at temperatures up to 2000°F (1093°C), using low carbon stainless steel with a maximum carbon content of 0.03, or incorporating stabilizing elements such as niobium or titanium.
6. Frictional Corrosion
The dissolution of metal through protective corrosion is caused by physical forces during wear or fracture. The severity of this effect depends on factors like pressure, speed, excessive vibration, and metal bending. Corrosion in pumps often takes the form of cavitation, while stress corrosion cracking can occur when high tensile stress and a corrosive environment are present.
When the tensile stress on a metal surface exceeds its yield point under static load, localized corrosion occurs, particularly in stressed areas. Preventive measures for such corrosion include early stress relief annealing, selecting suitable alloy materials, and implementing design solutions. Corrosion fatigue, on the other hand, refers to the degradation resulting from the combined effects of cyclic stress and corrosion.
Impact of Corrosion on Valves
Corrosion can affect the safety of workers, negatively impact the performance of valves, and disturb the production and plant operation of the chemical plant.
- Trigger Work Accidents
- Decreases Valve Performance
- Disturbance to Production & Plant Operation
- Costly – Frequent Replacements Required
Swissfluid as a Solution to the Corrosion Problem
If you need a solution for valve corrosion problems, Swissfluid can help you with durable valves made from quality materials that can withstand and ideal for high-risk corrosion environments. These valves have a tough PFA/PTFE lining that surpasses rubber, providing excellent resistance to corrosion and higher temperatures (up to 220°C).
Components that Makes Swissfluid Corrosion-Resistant
Swissfluid is a leading provider of corrosion resistance components. These components are designed with advanced materials and innovative technologies to ensure superior performance in corrosive environments. The PFA/PTFE material offers superior high-temperature resistance compared to PVC, PVDF, and GRPP.
The valves also feature a durable body made of corrosion-resistant Wrought Carbon (WCB) or we also have Stainless Steel which has better durability and chemical resistance than cast iron. The inner metal components, such as the ball, plug, or disc, are made of corrosion-resistant Stainless Steel, Duplex, ensuring high-grade performance.
Why Swissfluid?
Swissfluid is known for its expertise in specialized lined products specifically designed for highly corrosive or abrasive applications. Our valves and valve systems are engineered for exceptional durability, ensuring minimal maintenance and extended service life. By choosing Swissfluid, you can benefit from reliable and long-lasting solutions that result in low total cost of ownership.
We offer a range of Swissfluid valves including Ball, Plug, Butterfly, and Diaphragm valves. These valves are resistant to chemical corrosion and are readily available in our warehouse. If you’re interested or have any inquiries, please don’t hesitate to contact us via email at: sales@contromatic.co.id.
References:
- https://www.bcstvalve.com/what-is-the-valve-corrosive-and-its-harm-for-the-valve/
- https://qrcvalves.com/valve-corrosion/#:~:text=Exposure%20to%20Seawater%20and%20Dissimilar,further%20aids%20the%20electrochemical%20process.
- https://www.linkedin.com/posts/pt-contromatic-prima-mandiri_swissfluid-corrosion-resistant-activity-7062653473879691264-XkyV
