Sodium hydroxide, also known as caustic soda, is an important industrial product. It has a wide range of uses. It is a strong alkali. It does not corrode seriously at room temperature, but it will cause serious corrosion to many metals in the presence of high temperature and stress. Iron and steel can be used in dilute sodium hydroxide solution at room temperature, but it will corrode rapidly when the temperature or concentration increases. It is important to study the corrosivity of different alloys in sodium hydroxide solution for material selection.

　　2. 氫氧化鈉選材的依據(jù)

　　NaOH 是一種強(qiáng)堿，在常溫下腐蝕性不強(qiáng)，但在高溫和有應(yīng)力存在的情況下會(huì)對許多金屬產(chǎn)生嚴(yán)重腐蝕[1]。不同濃度的NaOH 溶液在不同溫度下其設(shè)備和管道的選材如圖１和表１所示。從圖１和表１可以看出，氫氧化鈉溶液的濃度為0～30％，若溫度低于50℃的情況下，Ⅰ類材質(zhì)的設(shè)備和管道通常是耐腐蝕的；而0％～30％氫氧化鈉溶液在Ⅱ類材質(zhì)的設(shè)備及管道中，在溫度為50～100℃的情況下，耐腐蝕性能較好。

　　It is a kind of strong alkali. It is not very corrosive at room temperature, but it will cause serious corrosion to many metals at high temperature and in the presence of stress. The material selection of equipment and pipes for different concentration solutions at different temperatures is shown in Fig. 1 and Table 11. From Fig. 1 and Table 1, it can be seen that the concentration of NaOH solution is 0-30%. If the temperature is lower than 50 C, the equipment and pipes of Class I material are usually corrosion-resistant, while the corrosion resistance of 0%-30% NaOH solution is better in the equipment and pipes of Class II material at the temperature of 50-100 C.

　　從選材圖1和表1還可以看出，，銀對NaOH 的耐蝕性好，其次是鎳。銀和鎳能耐所有濃度和溫度的NaOH，直到熔融狀態(tài)（480℃）。對于高溫、高濃度堿而言，好選用鎳及其合金（如因科鎳，蒙乃爾等）。不銹鋼對40％～50％以下的NaOH溶液可耐溫80～100℃，但不耐高濃度、高溫堿液。碳鋼在較稀的低溫NaOH溶液中耐腐蝕性能較好，可以在表面形成堅(jiān)實(shí)的氧化保護(hù)膜，且由于低廉，常常成為許多用戶的。

　　It can also be seen from the material selection figures 1 and 1 that the corrosion resistance of silver pairs is the best, followed by nickel. Silver and nickel can withstand all concentrations and temperatures until they melt (480 C). For high temperature and high concentration alkali, nickel and its alloys (such as Inco nickel, Monel, etc.) are the best choice. Stainless steel can withstand 80-100 C for solutions below 40%-50%, but not high concentration and high temperature alkali solution. Carbon steel has good corrosion resistance in relatively low temperature NaOH solution and can form a solid oxide protective film on the surface. Because of its low cost, it is often the first choice of many users.

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　　The above content is organized and published by potassium hydroxide manufacturers. More information can be consulted by clicking on our official website: http://www.yiqijieneng.cn.