Electrical performance of aluminium/copper bolted joints

The 1350 aluminium/copper bolted joint is fundamentally less secure than the all-aluminium connection. Differential expansion shearing force at the interface is considered to be a significant degrading influence. As a consequence, substantial clamping pressures are needed in addition to having regard to surface preparation and bolting torques. Although inert greases are used at the interface to restrict corrosion outdoors, they do not improve joint stability. A hard plating, such as nickel, on the copper surface is advantageous, but softer deposits (e.g. thick electrotin or silver) cause rapid deterioration and are best improve the stability of the bimetal joint and eliminate the need for interface cleaning.