ASTM G67 潮湿SO?腐蚀试验方法

ASTM G67-2013发行信息

标准号ASTM G67-2013

中文名用接触硝酸环境之后的重量损失来测定5XXX系列铝合金晶间腐蚀敏感性的标准试验方法 (NAMLT试验)

英文名Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test)

发布日期2013

实施日期

废止日期无

国际标准分类号77.120.10 (Aluminium and aluminium alloys)

发布单位US-ASTM

ASTM G67-2013适用范围

1.1本试验方法描述了5XXX系列铝合金的恒定浸没晶间腐蚀试验程序。

1.2本试验方法仅适用于锻造产品。

1.3本试验方法包括试样类型、试样制备、试验环境和暴露方法。

1.4以国际单位制表示的数值应视为标准。括号中给出的值仅供参考。

1.5本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前建立适当的安全和健康实践，并确定监管限制的适用性。

1.1 This test method describes a procedure for constant immersion intergranular corrosion testing of 5XXX series aluminum alloys.

1.2 This test method is applicable only to wrought products.

1.3 This test method covers type of specimen, specimen preparation, test environment, and method of exposure.

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.5 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.

4.1 This test method provides a quantitative measure of the susceptibility to intergranular corrosion of Al-Mg and Al-Mg-Mn alloys. The nitric acid dissolves a second phase, an aluminum-magnesium intermetallic compound (x03b2;Al-Mg), in preference to the solid solution of magnesium in the aluminum matrix. When this compound is precipitated in a relatively continuous network along grain boundaries, the effect of the preferential attack is to corrode around the grains, causing them to fall away from the specimens. Such dropping out of the grains causes relatively large mass losses of the order of 25 to 75 mg/cm2 (160 to 480 mg/in2), whereas, samples of intergranular-resistant materials lose only about 1 to 15 mg/cm2 (10 to 100 mg/in2). When the x03b2;Al-Mg compound is randomly distributed, the preferential attack can result in intermediate mass losses. Metallographic examination is required in such cases to establish whether or not the loss in mass is the result of intergranular attack.

4.2 The precipitation of the second phase in the grain boundaries also gives rise to intergranular corrosion when the material is exposed to chloride-containing natural environments, such as seacoast atmospheres or sea water. The extent to which the alloy will be susceptible to intergranular corrosion depends upon the degree of precipitate continuity in the grain boundaries. Visible manifestations of the attack may be in various forms such as pitting, exfoliation, or stress-corrosion cracking, depending upon the morphology of the grain structure and the presence of sustained tensile stress.3