Galvanic corrosion is a type of corrosion which occurs when two different metals are in contact with each other and an electrolyte. Different metals will have different electric potentials when connected in this way. This difference creates an electric current through the electrolyte. In fact, the action of galvanic corrosion is the principle with which batteries are made. Of course this is also the reason batteries have a shelf life. The action of this circuit degrades whichever metal has a lower electric potential. This is described as being less noble, whereas the metal with the higher potential is more noble. The degradation of the less noble metal eventually gets to the point that the circuit is broken by the oxides and salts created by the corrosion. This is the reason not only for a battery’s eventual death, but also for the way it dies, slowly losing electric potential because the anode (lower potential metal or connection) is slowly destroyed by the action of galvanic corrosion.
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To be clear, the difference between electronics and other electrical systems is that electronics include active components to control the flow of electricity, whereas non-electronic electrical systems use mechanical switches or relays. The development of the vacuum tube (the first active component invented) allowed for the creation of far more complex systems than was possible with prior technology. Then solid-state transistors allowed electronics to shrink to sizes unthinkable before. Certainly at this point it is trivial to say that electronics are ubiquitous in society today and will only continue to become more so in the coming years, all the way up to the singularity, at which point we will become our own technology. As electronics have developed through the years, they have been given increasingly more important tasks. From air traffic control to car computers to medical equipment to missile defense, systems which include electronics control and protect our lives everyday. Thus it is essential that we know how to maintain them, for which we must also know how they degrade.
Where the icky brown rusty corrosion is easy to see on ferrous metals (steels; iron based), corrosion on non-ferrous metals is less visually intrusive, but may be more debilitating. The electronics industry uses both ferrous and non-ferrous metals in their manufacturing. Many of the chassis and support structures may be made of steel, but the conductive non-ferrous metals used for electron pathways are typically copper, silver, aluminum, and/or their alloys.
Here are four problems that can occur from corrosive reactions to the non-ferrous metals in electronics and their assemblies: