Corrosion of valves, usually understood as valve metal materials in the chemical or electrochemical environment under the action of the destruction. As the "corrosion" phenomenon in metal and spontaneous interaction among the surrounding environment, therefore, how the environment around the metal with the use of isolation or more non-metallic composite materials, then become a common concern.
As we all know, metal corrosion damage on the valve's duration, reliability and service life has a considerable impact. The effect of mechanical and corrosive factors on the metal greatly increases the total wear on the contact surface. Total wear of friction surfaces during valve operation. In the operation of the valve, the friction of the surface due to the simultaneous mechanical action and metal and environmental chemical or electrochemical interaction results in wear and damage. On the valve, the pipeline of complex climatic conditions of work; oil, natural gas and oil water medium hydrogen sulfide, carbon dioxide and some organic acids to increase the destructive power of the metal surface, which quickly lose their ability to work.
Due to chemical corrosion of metals depends on the temperature, the friction parts of the mechanical load, lubricating materials contained in the sulfide and acid stability and media exposure duration and the process of catalytic metal nitride, Corrosion Erosion of material elements of the metal conversion speed and so on. Therefore, the metal valve anti-corrosion methods (or measures) and the application of synthetic materials valve, valve industry has become one of the topics of research.
A metal valve corrosion, can be understood as the coated metal valve to protect against corrosion protection layer conditions (such as paint, paint, lubricating materials and so on), whether the valve is in the manufacturingstoragetransport or in the whole process of its use are not subject to corrosion.
Metal valve anti-corrosion method depends on the required protection period, transportation and preservation conditions, valve construction features and materials, of course, to consider the economic effect of lifting the anti-corrosion.
Metal valves and parts anti-corrosion methods are mainly 4:
1, the volatile corrosion inhibitor into the vapor in the atmosphere (with the resistance of paper package, blowing air through the product chamber suppression etc.).
2, using blocked water and alcohol solution.
3, anti-corrosion (protective) material thin coated on the valve and its parts surface.
4, will be blocked thin film or polymer coating on the valve and its parts surface.
Note: the current valve manufacturer, the extensive use of lubricating materials and water resistance to dissolve flow to anti-corrosion.
Two, material valve application
Synthetic valves, in many corrosive conditions are superior to metal valves, first of all corrosion resistance, followed by net weight, as for its strength, depending on the shape, arrangement and quantity of reinforced fiber. Generally, the greater the percentage of fibers, the greater the strength of the synthetic material. In valve applications, the fiber content of the basic weight of 30%-40% range, and its chemical stability is mainly determined by the characteristics of the final product in bulk resin potting fiber. Valve in composite materials, its solid polymer body may be either thermoplastic (such as PVC- polyvinylidene fluoride, PPS- PPS, etc.) can also be a thermosetting resin (such as polyester, vinyl and epoxy resin). Thermosetting resin is better than thermoplastic in maintaining its strength under the condition of medium temperature (i.e. thermosetting resin has high thermal deformation temperature). Note: the determination of the thermal resistance of synthetic materials in the operating conditions is called the thermal deformation temperature.
At present, the most commonly used chemical process valves for the vinyl resin composite materials (thermal plastic material), the reinforced fiber chopped glass fiber (1/4 inches long) and chopped graphite fiber (1/4 inch). The following table compares the performance of the most widely used synthetic materials with the properties of corrosion resistant metals.
Glass reinforced vinyl base ink reinforced vinyl base ink reinforced PPS 316SS Hast-C
Tensile strength (Psi) 400060002600085000 90000
Flexural strength (Psi) 80001200035000 NA NA
Compression strength (Psi) 140001800021000 8500090000
Hot deformation temperature (F) 2957320520 NA NA
Thermal expansion coefficient (in/in/ DEG F) 15 * 10-6
15 * 10-6
13 * 10-6
6.3 * 10-6
9.9 * 10-6
Note: NA is not applicable (or invalid)
From the surface analysis, compared to synthetic materials and metal reinforced glass and graphite, the tensile strength is low, therefore, the synthetic material of the valve section would be affected by the high capacity should be thick with stiffeners in order to achieve the same performance with metal.
As the synthetic material valve corrosion resistance, high strength and light weight, making it in many metal or glass fiber reinforced plastic pipe system corrosive condition, more economical optional valve products. In chemical process conditions, the use of synthetic materials valve excellent prospects.
In the valve industry, the use of organic materials and synthetic materials, is not the traditional metal and non-metallic valve materials concept. (you can use the ceramic valve temperature from 400 DEG C to 1200 DEG C), plastic (with rust resistant characteristics), synthetic materials (has the characteristics of corrosion resistance, light weight, high strength), memory alloy (shape memory alloy or temperature memory alloy reversibility and high elasticity to manufacture valve etc.). New materials, is developing a large number of high-performance valve new products. new