On the inside, scale forms over time, reducing thermal conductivity.
Copper pipes are a very good option, however, their pricing policy and incompatibility with aluminum are very large minuses. If you put copper pipes, then guaranteed service life is at least 50 years. As soon as the heating system begins to function, the top of the pipes is covered with copper oxide, which helps to protect against corrosion. Their appearance is more attractive, which is a lot important. Thanks to a light mount, installing pipe from copper will not take much time. But among the large number of advantages, there are drawbacks: