Shielding performance of conductive elastomer gaskets

The shielding effectiveness of conductive elastomer gaskets has been shown to be significantly impaired by chromate conversion coatings and this is seen to be particularly bad with the silver plated aluminium filler sample tested. In the worst curve the improvement at high frequencies is probably due to the reducing capacitive reactance of the chromate film. The fact that the poor gasket performance under these conditions is not more widely reported is probably due to the fact that the back-up of metal to metal contact is usually present, making detection by means of bonding resistance checks alone impossible