Galvanic Corrosion and the Case for Composites
Anyone who has ever worked on an old steel-frame road bike with aluminum parts knows the “dissimilar metals” effect. The mix of aluminum parts and chromoly-steel led to some monstrous galvanic corrosion—the electrochemical action of two dissimilar metals in the presence of an electrolyte (salt sweat) and an electron conductive path. Such galvanic action is a principal corrosion problem in electrical interconnect systems. Specifically, the galvanic corrosion between the base metal of a part and its conductive plating. One way to solve this corrosion challenge is to specify composite thermoplastics for connectors and backshells. Composite thermoplastics offer unlimited corrosion resistance. Conversely, aluminum interconnect components
are always at risk from galvanic corrosion when their protective finish breaks down or gets damaged.Substituting composite plastic for the aluminum eliminates conditions required for this type of corrosion to occur. Glenair has a responsibility to deliver interconnect systems and hardware without “built-in” corrosion problems. To prevent corrosion problems in backshells, for example, engineers use their thorough
understanding of design and materials science to produce conductive, plated products which both prevent EMI and resist corrosion in harsh application environments. The simplest solution to this challenge by far is the specification of composite materials in place of metal.
Glenair innovative composite thermoplastics: a low-profile, split-shell banding backshell, 45° and 90° entry backshells for rectangular D-Sub connectors, and a cathodic-delamination-proof high-pressure underwater overmolded plug and receptacle.
Electro- and Electroless Plating Electro-depositing, or “electroplating,” is the coating of an object with a thin layer of metal using electricity. The metals most often used are gold, silver, chromium, copper, nickel, tin, cadmium, and zinc. The object to be plated, called the “work,” is usually a different metal, but can be the same metal or even a nonmetal, such as a composite thermoplastic. Electroplating usually takes place in a tank of solution containing the metal to be deposited on the work. When these electroplating chemicals dissolve, the atoms move freely, but lose one or more negatively-charged electrons and, as a result, become positively charged ions. Although ions are not visible to the naked eye, the solution may show some color; a nickel solution, for example, is emerald green. The object to be plated is negatively charged by an electrical source and attracts the positive metal ions, which coat the object, regain their lost electrons and become metal once again. Another process called electroless-deposited plating operates without using electricity. The action is purely chemical and, once started, is autocatalytic (it runs by itself). Electroless plating enables metal coating of other metals as well as nonconductive materials, such as plastics and ceramics. Composites and other non-conductive materials must be metalized in an electroless process before they can be electroplated.
QwikConnect • April 2023
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