Question

Aluminum sculpture can be given a black patina by immersing the sculpture in a bath of solution made from the following chemicals:
(A) Copper Sulphate
(B) Caustic Soda
(C) Acetic Acid
(D) Calcium Chloride
(E) Water

• A. (A), (B), (C), (D), (E)
• B. (A), (B), (E) and (D)
• C. (B), (C), (E) and (A)
• D. (B), (D) and (E) only

Hint:

Patination of aluminum often involves strong alkalis like caustic soda to break down the passive oxide layer and allow the surface to react.

Answer 1

The Correct Option is D

Step 1: Comprehend the patination's chemical process. Patination utilizes a chemical reaction on the metal's surface to modify its color and texture. For aluminum, a strong alkali or a particular salt solution is frequently applied.
Step 2: Examine the chemicals. Caustic Soda (Sodium Hydroxide) is a potent alkali that etches aluminum's surface, crucial in many blackening procedures. Water acts as the universal solvent. Additional chemicals serve as modifiers.
Step 3: Assess the combinations. A common chemical bath for creating a black smut on aluminum comprises a hot solution with caustic soda and other salts. The mixture of (B) Caustic Soda, (D) Calcium Chloride, and (E) Water yields a functional chemical solution for etching and coloring the aluminum surface. Alternative combinations are chemically less standard for achieving a black patina on aluminum.