Potential for Galvanic Corrosion between Carbon Fibers and Al Wires in ACCC/TW Conductor

Galvanic Corrosion and Composites. “Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in contact with a different type of metal and both metals are in an electrolyte [1].” Thus, corrosion of this type is always a concern when two different materials are to be in mutual contact. In the aerospace industry for instance, galvanic corrosion could occur when aircraft parts made from carbon fiber/epoxy composites (CF) are attached to metal parts of the airframe, particularly since carbon and aluminum are on opposite ends of the galvanic series [2,3]. Thus, when carbon is in direct contact with an Al alloy, the alloy will tend to corrode at a faster rate than it would if it were not coupled to the carbon. This raises serious concerns for aircraft performance and reliability (and for any application involving CF composites in contact with aluminum). Note that an electrolyte, such as humidity or salt water, is required for the galvanic process to occur. In fact, there are five requisite conditions that must be satisfied for composite-to-metal galvanic corrosion [3]: 1) an actively corroding metal, 2) an electrically conductive composite usually carbon fiber, 3) an electrical connection between the composite and the corroding metal, 4) salt water (electrolyte) and 5) oxygen. However, if any of these requirements are absent, galvanic corrosion will not occur. Instead, the components will corrode at rates that they naturally corrode when immersed in an electrolyte.