点腐蚀

2016-05-30 16:30:28

点蚀又称小孔腐蚀，是一种腐蚀集中在金属表面很小范围内并深入到金属内部甚至穿孔的孔蚀形态。具有自钝化特性的金属，如不锈钢、铝和铝合金等在含氯离子的介质中，经常发生点蚀。在许多含氯离子的介质中碳钢亦会出现点蚀现象。小孔腐蚀的蚀孔直径一般只有数十微米，但深度等于或远大于孔径。孔口多数有腐蚀产物覆盖，少数呈开放式（无腐蚀产物覆盖）。蚀孔通常沿着重力方向发展，一块平放在介质中的金属，蚀孔多在朝上的表面出现，很少在朝下的表面出现。

总体概况

点蚀是一种典型的局部腐蚀形态，具有较大的隐蔽性和破坏性。点蚀的发生和分布具有随机性，给评定点蚀敏感性的试验带来很大困难。点蚀研究具有重大的理论和应用价值。从应用角度出发，点蚀研究的目的有：评定材料发生点蚀的倾向；判断已发生点蚀的设备的剩余使用寿命；了解各种因素对发生点蚀的影响；发展新的耐点蚀材料；寻求防止点蚀的途经。从理论角度讲，点蚀研究的目的在于搞清点蚀发生和发展的机制。点蚀敏感性的试验评定方法可分为化学浸泡、电化学测试和现场试验三类。

详细介绍

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点蚀相关技术标准

标准名称：Standard Guide for Examination and Evaluation of Pitting Corrosion
标准编号：ASTM G46–94
实施日期： 2005-05-01
标准概述：This guide covers the selection of procedures that can be used in the identi?cation and examination of pits and in the evaluation of pitting corrosion to determine the extent of its effect.This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

标准名称：Standard Test Method for Electrochemical Critical Pitting Temperature Testing of Stainless Steels
标准编号：ASTM G150–99
实施日期： 1999-01-10
标准概述：This test method covers a procedure for the evaluation of the resistance of stainless steel and related alloys to pitting corrosion based on the concept of the determination of a potential independent critical pitting temperature （CPT）。This test methods applies to wrought and cast products including but not restricted to plate, sheet, tubing, bar, forgings, and welds.The standard parameters recommended in this test method are suitable for characterizing the CPT of austenitic stainless steels and other related alloys with a corrosion resistance ranging from that corresponding to solution annealed UNS S31600 （Type 316 stainless steel） to solution annealed UNS S31254 （6 % Mo stainless steel）。

标准名称：不锈钢三氯化铁点腐蚀试验方法
标准编号：GB/T 17897-1999
发布日期：1999-01-01
实施日期： 2000-08-01
标准概述：本标准规定了不锈钢三氯化铁点腐蚀试验方法的试样的制备、试验溶液、试验仪器和设备、试验条件和步骤、试验结果和试验报告。本标准适用于评价不锈钢在6%三氯化铁溶液中的耐点蚀性能。注：本试验方法所用的试验溶液，氧化性强，酸性强，氯离子含量较高，因此腐蚀性强。当材料在试验溶液中发生金属间化合物的溶解或有析出物时，往往会加速腐蚀。特别是合金素钛往往会加剧腐蚀。因此，用本试验方法来比较不同材料的耐点蚀性能，或者把实验数据与实际环境进行比较时，要注意本试验溶液的特性。

标准名称：Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution
标准编号：ASTM G48–03
实施日期： 2009-03-01
标准概述：These test methods cover procedures for the determination of the resistance of stainless steels and related alloys to pitting and crevice corrosion whenexposed to oxidizing chloride environments. Six procedures are described and identi?ed as Methods A,B,C,D,E,and F.