The interface resistance between a cadmium plated connector and an Alodined aluminum bracket

Many commercial applications require the bolting of a cadmium-plated connector to an Alodined aluminum bracket. The resistance of the interface between these two surfaces can become important because the shell of the connector and the Alodined aluminum bracket may be part of a ground path. In some cases, this interface resistance was low and stable. In other cases this interface was low, but almost immediately began to increase. The cause and extent of the increase in resistance is not well understood. The purpose of this research project was to understand why some interface resistance values were low and stable, while others were not stable. Material studies were conducted on the contact area. An automated contact resistance probe was used to determine the surface resistance of each surface. A statistical test of various connectors that were mounted to the aluminum bracket was conducted, The material studies revealed that the main area of contact, between the connector and bracket, was in a zone around the mounting holes. The conclusion from the contact resistance probe data was that the major cause of the interface resistance problem came from the Alodined surface. The statistical experimentation revealed that metallic particles could be added to the interface and could create a low and stable resistance through the connector and bracket interface.