A new system is being installed on HMS Belfast to help protect the ship's hull from corrosion.
The Second World War warship, which is permanently moored on the River Thames in London, is being fitted with a new self-regulated system which uses electricity to prevent rust building up.
The latest Cathodic Protection System monitors the water and adjusts to any changes by inserting titanium rods or anodes into the water.
A low voltage current is then passed through the rods with the water acting as a conductor - stopping rust from developing on areas where the paint on the hull might be damaged.
David Tresidder, from Beckett Rankine, who designed the system, said: "Corrosion is basically an electrical reaction and if we can reverse that, we can stop it from happening.
"So, by setting up a low voltage electrical field around the vessel, then we can stop corrosion as a reaction actually happening.
"We're putting anodes onto the dolphin structures that are here and they provide the low voltage current and we can connect the vessel as the other half of it.
"The conductor is the water of the Thames, set up an electrical current and through that mechanism, we can stop any corrosion that's happening on any bits of steel where the paint has actually failed."
The ship commissioned into the Royal Navy just before the start of World War Two in August 1939.
Just months later in November 1939, she was almost destroyed when a German magnetic mine sent her nearly three feet into the air.
HMS Belfast was left out of action for three years but re-emerged in 1942, equipped with the latest radar systems.
She went on to play a key role in the war, including D-Day.
The ship has been moored on the River Thames since 1971 where it has been used as a floating museum.
"This work today reminds us that the ship is a living being," said Nigel Steel, HMS Belfast historian.
"It's very important to keep it and maintain it in the best possible condition and today, the Cathodic Protection System does that for us so that we can remain confident that this is a visitor attraction which is safe and secure."
Work on HMS Belfast is expected to be finished before Christmas.