Copper is a very malleable and corrosion resistant alloy that is often used in many applications such as home heating, plumbing, marine engineering, shipbuilding, and other industrial processes for heat transfer. Copper is a very good conductor and relatively inexpensive. It can transfer heat up to 20 times faster than stainless steel so it is an excellent material to use for quick heating. One drawback however is that it is a soft material that can be prone to warping in a horizontal application. Over time, gravity and sedimentation buildup can warp the elements and affect its durability. The longer the immersion length, the more prone the heater will get to warping as a result of the additional weight.
Stainless steel has a property known as passivation that adds to its resilience against corrosion that protects it from rust and allows for a longer lifespan. The lifespan of copper is adversely affected from corrosion as the metal dissolves over time and affects its longer term thermal conductivity.