Corrosion of metal valves and the use of synthetic material valves
Corrosion in metal valves is typically defined as damage to the metal material due to chemical or electrochemical reactions with its surrounding environment. Since corrosion occurs naturally through the interaction between metal and the environment, the key challenge lies in either isolating the metal from its surroundings or replacing it with more durable, non-metallic synthetic materials. This has become a major concern in valve design and maintenance.
Metal corrosion significantly affects the lifespan, reliability, and performance of valves. The combined effects of mechanical wear and corrosion can lead to increased surface degradation. During operation, the friction surfaces of valves are constantly subjected to both mechanical stress and chemical or electrochemical interactions with the medium they handle. In harsh environments like oil, natural gas, or formation water, the presence of hydrogen sulfide, carbon dioxide, and organic acids accelerates the deterioration of metal components, reducing their functional effectiveness over time.
The extent of metal corrosion depends on several factors, including temperature, mechanical load on moving parts, the presence of sulfides in lubricants, acid resistance, exposure duration to the medium, and the catalytic role of the metal in nitriding processes. These variables influence how quickly corrosion occurs, making the development of anti-corrosion strategies and the adoption of synthetic valves increasingly important in the industry.
Anti-corrosion measures for metal valves involve applying protective coatings such as paints, pigments, or lubricants to shield them from environmental damage throughout their lifecycle—whether during manufacturing, storage, transportation, or operation. The choice of method depends on the required protection duration, shipping and storage conditions, the valve’s construction, and economic considerations.
There are four main methods for preserving metal valves:
1. Using volatile corrosion inhibitors in a sealed atmosphere (e.g., wrapping in corrosion-resistant paper or using air blowing to prevent contamination).
2. Applying water- or alcohol-based solutions that create a protective barrier.
3. Coating the valve surfaces with anti-corrosion materials.
4. Applying thin films or polymer coatings to protect the surface.
(Note: Many valve manufacturers currently use lubricants and water-resistant compounds for effective corrosion prevention.)
In addition to metal valves, synthetic material valves are gaining popularity due to their superior performance in aggressive environments. These valves are highly resistant to corrosion, lighter in weight, and their strength depends on the fiber content, alignment, and type used. Typically, fiber content ranges from 30% to 40%, and the chemical stability comes from the resin used in the composite. Common thermoplastic materials include PVC, PVDF, PPS, while thermosetting resins like polyester, epoxy, and vinyl ester are also widely used. Thermosetting resins offer better heat resistance compared to thermoplastics.
Currently, the most commonly used synthetic material for chemical process valves is glass or graphite-reinforced vinyl ester. These composites are known for their corrosion resistance, making them a cost-effective alternative to traditional metal or fiberglass piping systems in corrosive environments.
Synthetic valves have excellent potential in chemical processing applications. Alongside traditional materials, new innovations in ceramics, plastics, and memory alloys are expanding the possibilities for high-performance valves. These advanced materials enable the creation of valves with improved durability, flexibility, and resistance to extreme conditions, marking a significant evolution in valve technology.
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