What should be done to the surface of the pipe before brazing?

Before brazing, it is essential to remove surface oxides because these impurities can significantly hinder the adhesion of the filler metal to the base metal. Oxides can create a barrier that prevents proper wetting and bonding, leading to weak joints that may fail under stress or heat. By cleaning the surfaces thoroughly, you ensure that the molten brazing alloy can flow into the joint, creating a strong and durable bond.

Preparation methods often include using mechanical means, such as abrasion, or chemical cleaning agents to ensure that the surfaces are free from contaminants such as oil, grease, or oxidation. This step is critical in ensuring the success and integrity of the brazed joint.

Other choices relate to different aspects of preparation or support techniques that may be relevant in certain contexts, but removing surface oxides directly impacts the effectiveness of the brazing process and is a fundamental prerequisite for achieving strong joints.