原文：
在腐蚀性介质工况下的阀门，防腐蚀就是化工设备最关键的地方，如果不能正确地选择化工阀门的金属材料，稍有不慎，轻则损坏设备，重则造成事故甚至引发灾难。据有关统计，化工设备的破坏约有60%是由于腐蚀引起的，因此在化工设备选型时首先要注意选材的科学性。通常有一种误区，认为不锈钢是“{wn}材料”，不论什么介质和环境条件都捧出不锈钢，这是不正确的，也是很危险的。下面针对一些常用化工介质谈谈选材的要点： 1.硫酸介质　作为强腐蚀介质之一，硫酸是用途非常广泛的重要工业原料。不同浓度和温度的硫酸对材料的腐蚀差别较大，对于浓度在80%以上、温度小于80℃的浓硫酸，碳钢和铸铁有较好的耐蚀性，但它不适合高速流动的硫酸，不适用作泵阀的材料；普通不锈钢如304（0Cr18Ni9）、316（0Cr18Ni12Mo2Ti）对硫酸介质也用途有限。因此输送硫酸的泵阀通常采用高硅铸铁（铸造及加工难度大）、高合金不锈钢（20号合金）制造。氟塑料具有较好的耐硫酸性能，采用衬氟泵阀（F46）是一种更为经济的选择。 2.盐酸介质　决大多数金属材料都不耐盐酸腐蚀（包括各种不锈钢材料），含钼高硅铁也仅可用于50℃、30%以下盐酸。和金属材料相反，绝大多数非金属材料对盐酸都有良好的耐腐蚀性，所以内衬橡胶泵和塑料泵（如聚丙烯、氟塑料等）是输送盐酸的{zh0}选择。 3.硝酸介质　一般金属大多在硝酸中被迅速腐蚀破坏，不锈钢是应用最广的耐硝酸材料，对常温下一切浓度的硝酸都有良好的耐蚀性，值得一提的是含钼的不锈钢（如316、316L）对硝酸的耐蚀性不仅不优于普通不锈钢（如304、321），有时甚至不如。而对于高温硝酸，通常采用钛及钛合金材料。 4.醋酸介质　它是有机酸中腐蚀性最强的物质之一，普通钢铁在一切浓度和温度的醋酸中都会严重腐蚀，不锈钢是优良的耐醋酸材料，含钼的316不锈钢还能适用于高温和稀醋酸蒸汽。对于高温高浓醋酸或含有其它腐蚀介质等苛刻要求时，可选用高合金不锈钢或氟塑料泵。 5.碱（氢氧化钠）　钢铁广泛应用于80℃以下、30%浓度内的氢氧化钠溶液，也有许多石化工厂在100℃、75%以下时仍采用普通钢铁，虽然腐蚀增加，但经济性好。普通不锈钢对碱液的耐蚀性与铸铁相比没有明显优点，只要介质中容许少量铁份掺入，不推荐采用不锈钢。对于高温碱液多采用钛及钛合金或者高合金不锈钢。 6.氨（氢氧化氨）　大多数金属和非金属在液氨及氨水（氢氧化氨）中的腐蚀都很轻微，只有铜和铜合金不宜使用。 7.盐水（海水）　普通钢铁在氯化钠溶液和海水、咸水中腐蚀率不太高，一般须采用涂料保护；各类不锈钢也有很低的均匀腐蚀率，但可能因氯离子而引起局部性腐蚀，通常采用316不锈钢较好。 8.醇类、酮类、酯类、醚类　常见的醇类介质有甲醇、乙醇、乙二醇、丙醇等，酮类介质有丙酮、丁酮等，酯类介质有各种甲酯、乙酯等，醚类介质有甲醚、乙醚、丁醚等，它们基本没有腐蚀性，常用材料均可适用，具体选用时还应根据介质的属性和相关要求做出合理选择。另外值得注意的是酮、酯、醚对多种橡胶有溶解性，在选择密封材料时避免出错。 还有许多其它介质不能在此一一介绍，总之在选材时切不可随意和盲目，应多查阅相关资料或借鉴成熟经验。

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译文：
Condition of the valves in corrosive medium, corrosion is the most critical parts of chemical equipment, if not properly selected chemical valve metal materials, a little careless, at worst damage to the device, while in the accident and even lead to disaster . According to statistics, chemical equipment, about 60% of the damage caused due to corrosion, chemical equipment selection so pay attention when the first selection of the scientific. Usually there is a misunderstanding, that stainless steel is the "Universal", no matter what the media and environmental conditions is offering stainless steel, this is not true, and it is very dangerous. Below for some commonly used chemical medium to talk about the selection of points: 1. Sulfuric acid as one of strong corrosive medium, sulfuric acid is the use of a very wide range of important industrial raw materials. Sulfuric acid concentration and temperature corrosion of materials vary greatly, for more than 80% concentration, the temperature below 80 ℃ of concentrated sulfuric acid, carbon steel and cast iron has better corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid , not to be used as valve materials; ordinary stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) have limited use of the sulfuric acid. Therefore, sulfuric acid delivery valve is usually high silicon cast iron (casting and machining difficult), high alloy stainless steel (Alloy 20) manufacturing. Fluorine plastic has good resistance to sulfuric acid properties, using fluorine Valve (F46) is a more economical choice. 2. Hydrochloric must have patience to sit through most of hydrochloric acid corrosion of metal material (including stainless steel), containing molybdenum high silicon iron are only available for 50 ℃, 30% less hydrochloric acid. And metal materials contrary, the vast majority of non-metallic materials have good resistance to hydrochloric acid corrosion, the pump liner of rubber and plastic pumps (such as polypropylene, fluorine plastic, etc.) is the best choice for hydrochloric acid transport. 3. Nitric acid media most common metal corrosion in nitric acid was rapidly destroyed, stainless steel is the most widely used nitric acid-resistant materials, all concentrations of nitric acid at room temperature have good corrosion resistance, it is worth mentioning that the stainless steel containing molybdenum ( such as 316,316 L) of nitric acid corrosion resistance is not only no better than ordinary stainless steel (eg 304,321), and sometimes even better. For high-temperature nitric acid, usually titanium and titanium alloy materials. 4. Acetic acid medium is one of the most corrosive substances, ordinary steel in all the acetic acid concentration and temperature will be severe corrosion, acid-resistant stainless steel is an excellent material, but also 316 stainless steel containing molybdenum for high temperature and dilute acetic acid vapor. For the high temperature and high concentration of acetic acid, or contain other corrosive media such stringent requirements may make use of high alloy stainless steel or fluorine plastic pump. 5. Alkali (sodium hydroxide) steel is widely used in less than 80 ℃, 30% of the concentration of the sodium hydroxide solution, and many petrochemical plants in 100 ℃, 75% is still below the ordinary steel, although the corrosion increased, but the economy good. General corrosion resistance of stainless steel on the lye no significant advantages compared with cast iron, as long as the media were mixed to allow a small amount of iron, stainless steel is not recommended. For the high-temperature alkaline to use more titanium and titanium alloy or high alloy stainless steel. 6. Ammonia (ammonium hydroxide) Most of the metal and nonmetal in liquid ammonia and ammonia (ammonium hydroxide) in the corrosion were slight, not only the use of copper and copper alloys. 7. Salt water (sea water) normal steel in sodium chloride solution and sea water, salt water corrosion rate is not high, are generally required to use paint protection; all kinds of stainless steel has a very low corrosion rate, but may be caused by localized chloride corrosion, typically 316 stainless steel is better. 8. Alcohols, ketones, esters, alcohols, ethers common media are methanol, ethanol, ethylene glycol, propanol, etc., ketones medium with acetone, methyl ethyl ketone, etc., there are a variety of methyl esters of medium, ethyl ester, ether medium with ether, ethyl ether, butyl ether, etc., they basically did not corrosive materials can be used for the specific use of the property should also be under the media and related requirements to make reasonable choices. Also noteworthy was the ketone, ester, ether on a variety of rubber are soluble, the choice of sealing materials to avoid mistakes. There are many other media can not be introduced in the 11, when a word must not be arbitrary in the selection and blind, should be more access to relevant information or learn from mature experience.