Evaluation of different contact-aid compounds for aluminum-to-copper connections

Whether the contact-aid compounds commonly used for aluminum-to-aluminum connections can also be used for aluminum-to-copper joints is investigated. The evaluation is based on the contact-resistance-force relationship, spreading tendency, protection ability against fretting, and performance of lubricated bolted joints under current-cycling conditions. In addition, the effectiveness of bimetallic aluminum-copper transition contact plates, commonly used in Europe for jointing aluminum to copper, is also evaluated. The results show that contact-aid compounds exert large, but different, effects on the contact-resistance behavior and performance of bolted aluminum-copper joints under current-cycling conditions. This difference is seen in the higher stability of bolted joints lubricated with compounds rendering a lower initial contact resistance.