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在腐蚀性介质或腐蚀与力学因素共同作用下,所导致的金属某一部位腐蚀,称为局部腐蚀。多数局部腐蚀电池的阴极面积比阳极面积要大得多,腐蚀产物对金属无保护作用,虽然金属的总损失重量不大,但腐蚀危害性很大。例如,小孔腐蚀可导致材料蚀穿;晶间腐蚀可使材料强度大幅度降低;应力腐蚀破裂可在没有明显预兆的情况下突然发生严重事故;等等。由于金属腐蚀控制工程中出现较多的危害较大的大都是局部腐蚀,因而对其更好地认识和掌握是有所必要的。现将常见的某些金属局部腐蚀类型作一介绍。
In the corrosive medium or corrosion and mechanical factors together, the resulting corrosion of a certain part of the metal, known as local corrosion. The area of the cathode of most locally corroded batteries is much larger than the area of the anode. The corrosion products have no protective effect on the metal. Although the total weight of the metal is not heavy, the corrosion is very harmful. For example, small hole corrosion can lead to material erosion; intergranular corrosion can greatly reduce the strength of the material; stress corrosion cracking can abruptly cause serious accidents without obvious signs; and so on. Since most of the major hazards in metal corrosion control projects are localized corrosion, it is necessary to better understand and master them. The common types of local corrosion of metals are now introduced.