Silver Elastomeric Specification MIL-DTL-83528

Abstract

The contents reveal that the silver elastomeric EMI gasket (which is stated to provide environmental and shielding protection for DoD weapon systems) can have a short storage and useful life. Reference to Appendix A is given. The appendix outlines six of the paragraphs that need revisions to accurately describe the silver elastomeric products. The revised paragraphs deal with: (1) the shielding effectiveness test data can be highly inflated (the results of two tests illustrate that the test data can be inflated by more than 60 dB); (2) the storage life can be as little as 4–6 months (the specification provides information on how to store the silver elastomeric products. If the products are not stored as stipulated, the shelf life can be extremely short); and (3) as stipulated in the specification, silver elastomeric products are incompatible with flanged surfaces in the presence of moisture and salt fog environments. If the weapon systems containing these products are subjected to a moisture or salt fog environment, galvanic corrosion can nullify the shielding provided by the gaskets.

MIL-DTL-83528 Rev. G is a specification covering Silver Elastomeric EMI gaskets “approved for use by all departments and agencies of the department of defense” [1].

The document is a general specification to be used for purchasing silver elastomeric EMI gaskets for the purpose of providing environmental and shielding protection for Department of Defense (DoD) weapon systems. The silver elastomeric gaskets referenced in this specification can possess two (2) significant problems for the DoD. These problems are:

• 1. The gaskets can possess a relatively short shelf life (the ability to shield a weapon system from the effects of an electromagnetic wave can be compromised while sitting on the shelf.)

• 2. The gaskets can possess a relatively short useful life. The silver content of the gasket material when exposed to moisture or salt fog environments will create a galvanic corrosion between the gasket and the structural surface of a weapon system [2]. This galvanic corrosion will highly compromise the ability of the gaskets to provide the required shielding.

A full critique of MIL-DTL-83528 G verifies that the problems exist, and is contained in Appendix A.