A thermal storage system includes a container, a thermal exchange device, a first thermal storage material, and a second thermal storage material. The first thermal exchange device is disposed in the container. The first thermal storage material is disposed in the container and is spaced apart from the thermal exchange device. The second thermal storage material is also disposed in the container in contact with the thermal exchange device. The first and second thermal storage materials are immiscible. The second thermal storage material is less reactive with the construction material of the thermal exchange device as compared to the first thermal storage material. Optionally, a second thermal exchange device can be submerged in the second thermal storage material. The first thermal exchange device is configured to supply heat to the second thermal storage material and the second thermal exchange device facilitates extraction of heat from the second thermal storage material.