Which of the statements given below are correct with reference to corrosion:

(A) Corrosion covers the surfaces of metallic objects with oxides or other salts.
(B) In corrosion, a metal is oxidised by the loss of electrons to oxygen and results in the formation of oxides.
(C) Rust is hydrated ferric oxide.
(D) A sacrificial electrode is used to save an object from corrosion.

Choose the correct answer from the options given below.

(A), (B), (C) and (D)

The correct answer is Option (3) → (A), (B), (C) and (D)

Verification of each statement:

• (A) Corrosion covers the surfaces of metallic objects with oxides or other salts. → Correct. Corrosion products are usually oxides, hydroxides, carbonates, sulfides, etc. (e.g., rust, green patina on copper).
• (B) In corrosion, a metal is oxidised by the loss of electrons to oxygen and results in the formation of oxides. → Correct. Corrosion is an electrochemical redox process in which the metal acts as anode and undergoes oxidation (Fe → Fe²⁺ + 2e⁻), and oxygen (or H⁺) is reduced. The most common form is oxygen corrosion leading to oxides.
• (C) Rust is hydrated ferric oxide. → Correct. Chemical formula of rust is approximately Fe₂O₃·nH₂O or Fe₂O₃·xH₂O (hydrated ferric oxide).
• (D) A sacrificial electrode is used to save an object from corrosion. → Correct. This is cathodic protection using a sacrificial anode (e.g., Zn, Mg, Al) which corrodes instead of the protected metal (like iron in ships or pipelines).