Why are circuit breakers and contactors coated with silver?

Answer 1

AnswerA silver-cadmium alloy is used much of the time, due to pure silver being very soft and subject to pitting each time the electical circuit is broken. The addition of cadmium greatly increases the hardness of the silver, which does a good job of extending the lifetime of the silver. The cadmium also greatly reduces the loss of conduction when the silver does oxidize.

Silver is used because it is the most conductive metal we have discovered. It also resists oxidizing, only doing so in the presence of sulfur, some halogens, and both nitric and sulfuric acids. The sulfur in many foods is what makes real silverware tarnish...a thin coating of sulfide is formed.

http://www.tpub.com/content/navyict/14120/141200066.htm

http://www.daviddarling.info/encyclopedia/S/silver.HTML

AnswerI think silver is supposed to be a good conductor of electricity. ANSWER:It prevents the contact points from corrosion and oxidation. Its not silver, its a mixture of tin and lead called solder. AnswerSilver is the best metallic electrical conductor...until it tarnishes (oxidizes)...at which point it becomes a rather poor conductor. Plated contacts are usually coated with Gold, which is almost as good a conductor as silver, but it's oxidized form still conducts about as well as pure gold. As for solder, it's usually a lead/tin alloy in electronics work, but can also be made with small amounts of silver as well. Lead in solder has been banned for piping where potable water is carried in the US. Answer: They're not.The issue isn't one of picking a metal or metal alloy that conducts well, but one that will resist damage or pitting due to electric arcing. Alloys with tungsten are often used. There are some other metals which can be alloyed to make arc resistant contacts, and they're all pretty exotic ones. Silver is the best metallic conductor at room temperatures under normal conditions, but switch contacts don't operate under "normal conditions" when they are opening and closing regularly.

When a current carrying contact set (like in a switch or circuit breaker) comes open, an arc will begin across the forming gap. This arc will continue for a short while as the contacts get farther apart and eventually will be extinguished. The arc will cause a bit of damage to the contact surface for that little bit that it's happening. Soft metals like silver, gold, copper and aluminum will get pounded by the arc. It will shred them in such a short time that it isn't worth building a contact set with them, at least not on a contact set that is going to get a lot of work opening and closing.

Answer 2

Silver is a very good conductor of electricity.