Which metal finishing method deposits metal onto a surface by electrolytic deposition?

Which metal finishing method deposits metal onto a surface by electrolytic deposition?

• A. Dip coating
• B. Powder coating
• C. Electroplating
• D. Baking

Answer: (C)

This question tests electroplating, a process where a metal coating is built up on a surface using electricity. In electroplating, the object to be coated acts as the cathode in an electrolytic cell, while a solution containing ions of the coating metal serves as the electrolyte. When direct current passes through, metal ions are reduced at the cathode and deposit as a metallic layer on the object's surface. The anode can be made of the coating metal, slowly dissolving to replenish ions, or it can be inert if ions are supplied separately. The thickness of the deposit is controlled by current density and time, allowing precise control over the coating amount. This method is used to improve appearance, corrosion resistance, hardness, or wear properties. By contrast, dip coating involves submerging the object in a liquid coating, powder coating applies a dry powder that is electrostatically charged and cured, and baking is simply a heat-curing step rather than depositing metal.

This question tests electroplating, a process where a metal coating is built up on a surface using electricity. In electroplating, the object to be coated acts as the cathode in an electrolytic cell, while a solution containing ions of the coating metal serves as the electrolyte. When direct current passes through, metal ions are reduced at the cathode and deposit as a metallic layer on the object's surface. The anode can be made of the coating metal, slowly dissolving to replenish ions, or it can be inert if ions are supplied separately. The thickness of the deposit is controlled by current density and time, allowing precise control over the coating amount. This method is used to improve appearance, corrosion resistance, hardness, or wear properties. By contrast, dip coating involves submerging the object in a liquid coating, powder coating applies a dry powder that is electrostatically charged and cured, and baking is simply a heat-curing step rather than depositing metal.