金属覆盖层 金和金合金电镀层的试验方法 第2部分:混合流动气体(MFG)环境试验

[中文适用范围]： ISO 4524 的这一部分提供了进行混合流动气体 (MFG) 环境测试的程序，涉及暴露于受控数量的腐蚀性气体混合物。 它描述了所需的设备以及气体、温度和湿度控制的方法，使测试能够以可重复的方式进行。 再现性是通过使用控制试样来测量的，其腐蚀膜通过质量增益、库仑分析或通过各种电子和X射线束分析技术来评估。 再现性也可以通过使用电阻或质量频率变化方法的原位腐蚀速率监测器来测量。 MFG 测试可用于： ——评估新型电接触金属化由于环境暴露于测试腐蚀性气体而对退化的敏感性； ——评估可作为腐蚀性气体进入屏障的连接器外壳的屏蔽能力； ——评估其他连接器材料（例如塑料外壳）对测试腐蚀性气体降解的敏感性。 MFG 测试通常不： ——用作孔隙率测试（有关孔隙率测试的指导，请参见 ISO 10308，金属涂层 — 孔隙率测试回顾）； ——适用于故障机制不是污染物气体腐蚀的情况，例如镀锡可分离触点。 [外文原描述]： This part of ISO 4524 provides procedures for conducting mixed flowing gas (MFG) environmental tests involving exposures to controlled quantities of corrosive gas mixtures. It describes the required equipment and the methods for gas, temperature and humidity control that enable tests to be conducted in a reproducible manner. Reproducibility is measured through the use of control coupons the corrosion films of which are evaluated by mass gain, coulometry or by various electron and X-ray beam analysis techniques. Reproducibility can also be measured by in situ corrosion rate monitors using electrical resistance or mass frequency change methods. MFG tests can be used to: _ evaluate novel electrical contact metallization for susceptibility to degradation due to environmental exposure to the test corrosive gases; _ evaluate the shielding capability of connector housings that may act as a barrier to the ingress of corrosive gases; _ evaluate the susceptibility of other connector materials such as plastic housings to degradation from the test corrosive gases. MFG tests are not normally: _ used as porosity tests (for guidance on porosity testing, see ISO 10308, Metallic coatings — review of porosity tests); _ applicable where the failure mechanism is other than pollutant gas corrosion such as in tin-coated separable contacts.