腐蚀是形成阀门损坏的重要元素之一。在阀门防护中,阀门防腐是思索的重要问题。阀门腐蚀终究为何?阀门该如何停止防腐?耐腐蚀阀门的选用又有何根据?一同来看看!
Corrosion is one of the important elements that cause valve damage. In valve protection, valve corrosion prevention is an important issue to consider. Why is the valve corroded after all? How should the valve stop corrosion prevention? What is the basis for the selection of corrosion-resistant valves? Come and have a look!
阀门腐蚀方式
Valve corrosion mode
金属的腐蚀主要是化学腐蚀和电化学腐蚀惹起的,非金属资料的腐蚀普通是直接的化学和物理作用惹起的毁坏。
The corrosion of metals is mainly caused by chemical corrosion and electrochemical corrosion. The corrosion of non-metallic materials is generally caused by direct chemical and physical effects.
1.化学腐蚀
1. Chemical corrosion
四周介质在不产生电流条件下,直接与金属起化学作用,而使其毁坏,如高温枯燥气体和非电解溶液对金属的腐蚀。
Under the condition that no current is generated, the surrounding medium directly reacts with the metal and destroys it, such as the corrosion of metal by high-temperature dry gas and non electrolytic solution.
2.电化学腐蚀
2. Electrochemical corrosion
金属与电解质相接触,产生电子活动,而使本身在电化学作用遭受毁坏,这是腐蚀的主要方式。
The main way of corrosion is that the metal contacts with the electrolyte and produces electronic activities, which destroys itself in the electrochemical action.
常见的酸碱盐溶液腐蚀、大气腐蚀、土壤腐蚀、海水腐蚀、微生物腐蚀、不锈钢的点腐蚀和缝隙腐蚀等等,都是电化学腐蚀。
The common acid-base salt solution corrosion, atmospheric corrosion, soil corrosion, seawater corrosion, microbial corrosion, spot corrosion and crevice corrosion of stainless steel are all electrochemical corrosion.
电化学腐蚀不只发作于能够起化学作用的两种物质之间,而且还由于溶液的浓度差、四周氧气的浓度差、物质构造的微小差异等等缘由,产生电位的差别,而取得腐蚀的动力,使电位低、处于阳板位置的金属受损失。
Electrochemical corrosion occurs not only between two substances that can play a chemical role, but also due to the concentration difference of the solution, the concentration difference of oxygen around, the slight difference of material structure and other reasons, resulting in the difference of potential, and obtaining the power of corrosion, so that the metal with low potential and in the anode position is lost.
9大防腐措施
9 major anti-corrosion measures
1.依据腐蚀介质选用耐蚀资料
1. Select corrosion resistance data according to corrosion medium
在消费实践中,介质的腐蚀是十分的复杂的,即便在用一介质中运用的阀门资料一样,介质的浓度、温度、压力不同,介质对资料腐蚀也不一样。介质温度每升高10℃,腐蚀速度约增加1~3倍。
In consumption practice, the corrosion of medium is very complex. Even if the valve data used in a medium is the same, the corrosion of medium to data is different with the concentration, temperature and pressure of medium. The corrosion rate increases by about 1-3 times when the medium temperature increases by 10 ℃.
介质浓度对阀门资料腐蚀影响很大,如铅处在浓度小的硫酸中,腐蚀很小,当浓度超越96%时,腐蚀急剧上升。而碳钢相反,在硫酸浓度为50%左右时腐蚀更严重,当浓度增加到6%以上时,腐蚀反而急剧降落。
The medium concentration has a great impact on the corrosion of valve data. For example, the corrosion of lead in sulfuric acid with small concentration is very small. When the concentration exceeds 96%, the corrosion rises sharply. On the contrary, the corrosion of carbon steel is the most serious when the concentration of sulfuric acid is about 50%. When the concentration increases to more than 6%, the corrosion decreases sharply.
有如铝在浓度80%以上的浓硝酸中腐蚀性很强,但在中、低浓度的硝酸中腐蚀反而严重。不锈钢虽说对稀硝酸耐蚀性很强,但在95%以上的浓硝酸中腐蚀反而加重。
For example, aluminum is highly corrosive in concentrated nitric acid with a concentration of more than 80%, but it is severely corroded in medium and low concentrations of nitric acid. Although stainless steel has strong corrosion resistance to dilute nitric acid, the corrosion is aggravated in more than 95% concentrated nitric acid.
从以上几例能够看出,正确选用阀门资料应依据详细状况,剖析各种影响腐蚀要素,按有关防腐手册选用资料。
From the above examples, it can be seen that the correct selection of valve data should be based on the detailed situation, analyze various factors affecting corrosion, and select data according to the relevant anti-corrosion manual.
2.采用非金属资料
2. Use non-metallic materials
非金属耐腐蚀性,只需阀门运用温度和压力契合非金属资料的请求,不但能处理腐蚀问题,而且可俭省贵重金属。
Non metallic corrosion resistance is excellent. As long as the application temperature and pressure of the valve meet the requirements of non-metallic data, it can not only deal with corrosion problems, but also save precious metals.
阀门的阀体、阀盖、衬里、密封面等常用非金属资料制造,于垫片,填料主要死非金属资料制造的。
The valve body, bonnet, lining, sealing surface and other commonly used non-metallic materials are manufactured. As for gaskets, fillers are mainly manufactured from non-metallic materials.
用聚四氟乙稀、氯化聚醚等塑料、以及用自然橡胶、氯丁橡胶、丁晴橡胶等橡胶做阀门衬里,而阀体、阀盖主体是普通铸铁、碳钢制成。即保证了阀门强度,又保证了阀门不受腐蚀。
The valve is lined with polytetrafluoroethylene, chlorinated polyether and other plastics, as well as natural rubber, neoprene, nitrile rubber and other rubbers, while the body and bonnet are made of ordinary cast iron and carbon steel. It not only ensures the strength of the valve, but also ensures that the valve is not corroded.
夹管阀也是依据橡胶的耐腐蚀性能和优良变性能而设计出来的。如今越来越对的用尼龙、聚四氟乙稀等塑料,用自然橡胶和合成橡胶做各种各样的密封面,密封圈,用于各类阀门上。
The pinch valve is also designed based on the excellent corrosion resistance and excellent denaturation of rubber. Nowadays, nylon, polytetrafluoroethylene and other plastics, natural rubber and synthetic rubber are increasingly used to make various sealing surfaces and rings for all kinds of valves.
这些用作密封面的非金属资料,不但耐腐蚀性好,而且密封性能好,特别适于带颗粒介质中运用。当然,它们的强度和耐热性都较低,应用的范围遭到限制。
These non-metallic materials used as sealing surfaces have not only good corrosion resistance, but also good sealing performance, and are especially suitable for use in media with particles. Of course, their strength and heat resistance are low, and the scope of application is limited.
柔性石墨的呈现,使非金属进入了高温范畴,处理了长期难以处理的填料和垫片泄露问题,而且是很好的高温光滑剂。
The appearance of flexible graphite makes non-metallic materials enter the high-temperature category, which solves the problem of packing and gasket leakage that is difficult to deal with for a long time, and is a good high-temperature smoothing agent.
常用非金属资料适用工况:
Applicable working conditions of common non-metallic materials:
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