When preparing a 50 mm (2 inch) copper pipe for soldering, after reaming the end, what is the primary purpose of properly cleaning the outside surface of the pipe and the inside of the fitting?

Question: When preparing a 50 mm (2 inch) copper pipe for soldering, after reaming the end, what is the primary purpose of properly cleaning the outside surface of the pipe and the inside of the fitting?

Answer options:

• To reduce the risk of galvanic corrosion
• To prevent thermal expansion during heating ✅ To ensure proper capillary action of the solder
• To increase the surface area for solder adherence

Correct answer: To ensure proper capillary action of the solder

Explanation: Proper cleaning (sanding or wire brushing) of copper surfaces is essential for successful soldering because it removes oxides and contaminants, allowing the molten solder to flow effectively into the joint via capillary action. While galvanic corrosion is a concern with dissimilar metals, cleaning is directly for solder flow, not expansion or solely increasing surface area.