Which method is used to provide a sacrificial electrode of another metal (like Mg, Zn, etc.) which corrodes itself but saves the object?

Electrochemical method

The correct answer is: 2. Electrochemical method

The method used to provide a sacrificial electrode of another metal (like Mg, Zn, etc.) that corrodes itself but saves the object from corrosion is the electrochemical method.

This process is known as sacrificial protection or cathodic protection. In sacrificial protection, a more active metal (like Mg or Zn) is connected to the object that needs protection (such as iron or steel). The more active metal acts as a sacrificial anode and undergoes corrosion instead of the object. As a result, the object is protected from corrosion.

Here's how it works:
i. The more active metal (e.g., Mg or Zn) is connected to the object that needs protection, and both are submerged in an electrolyte (usually a conducting solution like water or soil).

ii. The more active metal, being the anode, starts to corrode and releases electrons into the solution. This anodic corrosion process forms metal ions (e.g., Mg^2+ or Zn^2+) in the solution.

iii. The metal ions in the solution move towards the object that needs protection (the cathode) and gain electrons from it. This cathodic reaction reduces the metal ions back to solid metal, preventing the object from corroding.

iv. The sacrificial anode (Mg or Zn) continues to corrode over time, sacrificing itself to protect the object from corrosion.

This electrochemical method of using a sacrificial electrode is widely used to protect structures like pipelines, ships, offshore platforms, and other metal structures exposed to corrosive environments.

Option 1, "Electrolytic method," is not correct as the electrolytic method involves using an external electric current to drive a non-spontaneous chemical reaction, while sacrificial protection is a spontaneous electrochemical process.

Option 3, "Photolytic method," is not relevant to sacrificial protection, as the photolytic method involves using light energy to drive chemical reactions.

Option 4, "All of these," is incorrect because only option 2 (Electrochemical method) accurately describes the technique used for sacrificial protection.

Therefore, the correct answer is option 2: Electrochemical method.