What Is Tinned Copper Wire?

Copper wires are some of the most commonly used components in electrical work. Whether the job involves power generation, telecommunications or simple circuitry, copper-based components often play a key part in the project. Despite all its versatility and its relatively low cost, regular copper wire is not perfect for every situation. In certain conditions, copper wire must be specially treated to remain effective.

Copper is the second most conductive metal in the world behind silver, but due to its abundance and how easy it is to work with, copper is considered the standard in electrical work. Copper is also the standard by which all other conductive metals are judged. In 1913, the International Electro-Technical Commission set its conductivity at 100 percent of the International Annealed Copper Standard (IACS). The metal resists galvanic corrosion – the gradual deterioration of one metal in electrical contact with another metal – and is durable enough that it avoids stretching, nicks and breaks. However, copper is not invincible.

If you've ever seen the Statue of Liberty, you've seen oxidized copper. In exceptionally humid climates, such as on the coastline, in swampy southern areas of the U.S., or in highly acidic soils, copper reacts to water, oxygen or sulfur in the environment and degrades into a semiconductor. In other words, the copper becomes far less efficient at moving electricity through itself. This problem is most often solved by a process called tinning.

When you apply a thin coating of tin to bare copper wire, either by dipping the copper in molten metal or by using an electric current to bind the tin to the copper, you create what is known as tinned copper wire. Tinned copper wire is just as conductive as bare copper wire, but the thin layer of tin helps the wire resist corrosion. Tinned copper wire can last up to 10 times longer than its non-tinned counterpart, and because solder is composed primarily of tin, tinned wire is incredibly easy to solder. Tinned copper wire is particularly useful in industrial cranes, subways and marine projects where the tin coat makes the wire more resistant to water.

Despite the many benefits of tinned wire, it is not always the right wire for the job. Tinned copper wire is more expensive than its non-tinned counterpart and can cost as much as 30 percent more than basic, bare copper wire. In environments where acidic soil, high heat or high humidity are not concerns for a project, non-tinned copper wire works just as well.