Why are inner lining of hot water geysers made up of copper ?

The inner lining of hot water geysers is made of copper primarily because copper does not react with water or steam, even at high temperatures [c4]. While copper is an excellent conductor of heat and electricity [t1][t3], its chemical stability in the presence of steam is the critical factor for the durability of the inner tank. Unlike iron, which reacts with steam to form iron oxide and hydrogen, copper remains unreactive, preventing corrosion and structural failure of the geyser [t2]. Additionally, copper's high thermal conductivity (approximately 401 W/m·K) ensures efficient heat transfer to the water, reducing energy consumption [t3]. Although copper is a good conductor of both heat and electricity, the specific choice for the 'lining' in contact with hot water and steam is dictated by its corrosion resistance and lack of reactivity with steam [t2][c4].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.9 > p. 42
2. [2] https://www.sciencedirect.com/topics/engineering/oxygen-free-high-conductivity-copper