What does the sacrificial anode technique involve?

The sacrificial anode technique involves using a more reactive metal to protect a less reactive metal from corrosion. This technique works by intentionally allowing the less reactive metal (such as iron or steel) to corrode at a slower rate than the sacrificial anode, which is usually made of a more reactive metal like zinc, magnesium, or aluminum. When the sacrificial anode is installed, it will corrode preferentially, thereby protecting the metal structure it is attached to.

In practical applications, this technique is often used in various industries, including marine and construction, to extend the lifespan of structures and vessels. The sacrificial anode is typically bolted or attached to the structure, allowing it to corrode instead of the structure itself. This makes the option regarding reactive blocks bolted to a metal structure relevant, as it describes one of the methods of implementing the sacrificial anode technique.

The other methods listed, such as coating the metal with oil or using electrical currents, describe different corrosion protection methods, such as barrier protection and cathodic protection, respectively, which do not involve the sacrificial action of a more reactive metal.