Table 3: Corrosion Potentials for Metals and Gasket Materials
表3：金属和垫片材料的腐蚀能力
Corrosion Potentials of Various Metals and EMI Gasket Materials (in 5% NaCl at 21oC, after 15 minutes immersion)
各种金属和 EMI 材料的腐蚀能力（在 5% 的 NaCl 溶液中浸泡 15 分钟后，溶液温度 21oC）
Material 材料 Ecorr vs. SCE* (Millivolts)
Ecorr vs. SCE* (毫伏)
Pure Silver 纯银 –25
Silver-filled elastomer 含银橡胶 –50
Monel mesh 蒙耐金属网 –125
Silver-plated-copper filled elastomer
含镀银铜的橡胶 –190
Silver-plated-aluminum filled elastomer
含镀银铝的橡胶 –200
Copper 铜 –244
Nickel 镍 –250
Tin-plated Beryllium-copper 镀锡铍铜 –440
Tin-plated copper-clad steel mesh
镀锡包铜钢网 –440
Aluminum* (1100) 铝* (1100) –730
Silver-plated-aluminum filled elastomer (die-cut edge)
含镀银铝的橡胶（模切边） –740
*Standard Calamel Electrode. Aluminum Alloys approximately –700 to –840 mV vs. SCE in 3% NaCl. Mansfield, F. and Kenkel, J.V., “Laboratory Studies of Galvanic Corrosion of Aluminum Alloys,” Galvanic and Pitting Corrosion – Field and Lab Studies, ASTM STP 576, 1976, pp. 20-47.
*标准 Calamel 电极棒。铝合金在 3% 的 NaCl溶液中约-700 至 840 mV vs SCE。Mansfield, F. 和 Kenkel, J.V.，“铝合金电化腐蚀的试验室研究”，电化和点蚀 － 现场和试验室研究，ASTM STP 576, 1976, 20-47 页。
Figure 5d compares the electrical stability of several conductive elastomers before and after salt fog exposure. In general, silver-containing elastomers are more electrically stable in a salt fog environment than nickel-containing elastomers.
图 5d 中对比显示了多种导电橡胶在接触起盐雾前后的电气稳定性。一般而言，含银橡胶在盐雾环境中的电气稳定性要优于含镍橡胶。
Design Guides for Corrosion Control
腐蚀控制设计指南
The foregoing discussion is not intended to suggest that corrosion should be of no concern when flanges are sealed with silver-bearing conductive elastomers. Rather, corrosion control by and large presents the same problem whether the gasket is silver-filled, Monel wire- filled, or tin-plated. Furthermore, the designer must understand the factors which promote galvanic activity and strive to keep them at safe levels. By “safe”, it should be recognized that some corrosion is likely to occur (and may be general-ly tolerable) at the outer (unsealed) edges of a flange after long-term exposure to salt-fog environments. This is especially true if proper attention has not been given to flange materials and finishes. The objective should be control of corrosion within acceptable limits.
前面所述内容的目的并不是建议当使用含银导电橡胶密封凸缘时，不需要考虑腐蚀问题。相反，无论对于含银垫片还是填有蒙耐金属网的垫片或镀镍垫片，腐蚀控制都是需要面对的一个非常重要的问题。此外，设计人员必须了解哪些因素会促进电化反应，并尽量将其保持在安全水平。所谓“安全”是指，当凸缘长时间暴露于盐雾环境中时，凸缘的外边缘处（未密封的边缘）可能会发生一些腐蚀现象（大体可以接受的）。特别是当对凸缘材料和表面处理注意不够时更是如此。我们的目标应该是将腐蚀控制在可接受的极限范围内。
The key to corrosion control in flanges sealed with EMI gaskets is proper design of the flange and gasket (and, of course, proper selection of the gasket material). A properly designed interface requires a moisture-sealing gasket whose thickness, shape and compression-deflection characteristics allow it to fill all gaps caused by uneven or unflat flanges, surface irregularities, bowing between fasteners and tolerance buildups. If the gasket is designed and applied correctly, it will exclude moisture and inhibit corrosion on the flange faces and inside the package.
对于使用 EMI 垫片密封的凸缘，控制腐蚀的主要方法是正确设计凸缘和垫片（当然，包括正确地选择垫片材料）。对于设计合理的界面，要求防潮密封垫片的厚度、形状和压紧变形特性能够使其填实因凸缘不平整、表面不规则、紧固件之间的翘曲和公差累积造成的所有间隙。如果垫片设计和使用方法正确，其将阻碍湿气进入，防止凸缘面和内部仪器组件发生腐蚀现象。
华译网上海翻译公司曾经翻译过大量有关腐蚀控制设计指南资料文件，Beijing Chinese Subtitling Translation Service Agency has translated many technical documents about Design Guides for Corrosion Control.
Bare aluminum and magnesium, as well as iridited aluminum and magnesium, can be protected by properly designed conductive elastomer gaskets. It is important to note that magnesium is the least noble structural metal commonly used, and a silver-filled elastomer in contact with magnesium would theoretically produce an unacceptable couple.
对于裸露的铝和镁及镀有铬层的铝和镁，可通过设计正确的导电橡胶垫片提供保护。需要重点说明的是，镁是常用的最次贵结构金属，含银橡胶与镁接触后，在理论上讲，会形成不可接受的组合。
Some specific design suggestions for proper corrosion control at EMI flanges are:
针对 EMI 凸缘的腐蚀控制设计建议包括以下：
1. Select silver-plated-aluminum filled elastomers for best overall sealing and corrosion protection against MIL-DTL-5541F, Type I, Class 3 coated aluminum. CHOSEAL 1298 material offers more corrosion resistance than any other silver-filled elastomer (see Figure 6).
对于做有 MIL-DTL-5541F， I 型 3 类涂层的铝材，选用含镀银铝的橡胶材料可提供最佳的整体密封和防腐蚀效果。CHOSEAL 1298 材料较其他含银橡胶而言，可提供更好的耐腐蚀性（见图 6）。
2. For aircraft applications, consider “seal-to-seal” designs, with same gasket material applied to both flange surfaces (see Figure 7).
对于航空应用，考虑采用“密封－密封”型设计，即在两个凸缘表面上均使用相同的垫片材料（见图 7）。
3. To prevent corrosion on outside edges exposed to severe corrosive environments, use dual conductive/ non-conductive gaskets or allow the non-conductive protective paint (normally applied to outside surfaces) to intrude slightly under the gasket (see Figure 8).
为防止暴露于严重腐蚀性环境中的外缘发生腐蚀，采用双导电/非导电垫片，或让不导电的保护漆层（一般涂装于外部表面上）稍稍浸入至垫片下面（见图 8）。
4. If moisture is expected to reach the flange interfaces in Class C (marine) environments, flange surfaces should be coated or plated to make them more compatible with the EMI gasket material. XXXX ’ CHO-SHIELD 2000 series coatings are recommended for silver-filled elastomer or Monel wire gaskets, and tin plating for tin-plated gaskets.
在 C 类（近海）环境中，如果凸缘交界面上可能会沾上湿气，则应对凸缘表面进行涂装或电镀处理，以使其能够与 EMI 垫片材料更加相容。对于含银橡胶或蒙耐金属网垫片，建议采用 XXXX 公司的 CHO-SHIELD 2000 系列涂层，对于镀锡垫片，建议进行镀锡处理。
Figure 6. Comparison of corrosion results obtained from CHO-SEAL? 1298 conductive elastomer (left) and pure silver-filled elastomer (right) mated with aluminum after 168 hours of salt fog exposure.
图6 与铝相配合的CHO-SEAL? 1298导电弹性体（左）和纯银填充的弹性体（右）暴露于盐雾环境下168小时后或获得的腐蚀结果对比。
Figure 7. “Seal-to-seal” design incorporating CHO-SEAL? 1287 conductive silver-aluminum fluorosilicone gaskets on both mating flange surfaces. Gaskets are bonded and edge sealed to prevent moisture from entering the gasket/flange area.
图 7. “密封－密封”设计，在相配合的两个凸缘表面上均使用了 CHO-SEAL? 1287 型导电银－铝氟硅氧烷垫片。垫片均粘合在一起，同时边缘密封，以防止湿气进入垫片/凸缘结合区域。
Figure 8. Non-Conductive Paint Intrudes Slightly Under Gasket to Provide Edge Protection
图 8. 稍稍浸入至垫片下面的非导电漆，用于提供边缘保护 |
