Metal Surface Treatment Processes

The question asks to identify the process used for the surface treatment of metals among the given options.

Analyzing Metal Treatment Options

Let's examine each option:

• Soldering: This is a joining process used to bond two metal pieces together using a filler metal. It is not primarily a surface treatment method.
• Thermoplating: This term likely refers to thermal plating or related thermochemical coating processes. Processes like hot-dip galvanizing or thermal spraying are used to apply a protective or functional layer to the metal surface, qualifying as surface treatment.
• Extrusion: This is a metal forming process used to create objects with a fixed cross-sectional profile by forcing material through a die. It shapes the metal but is not a surface treatment.
• Riveting: This is another mechanical joining process that uses rivets to fasten components together. It does not alter the metal's surface properties as a treatment.

Based on the analysis, Thermoplating (or related thermal coating processes) is the method specifically used for the surface treatment of metals.