Final answer:
Welding can cause oxidation, which degrades the corrosion resistance of metals. This degradation occurs due to the reaction between the metal and substances like oxygen, leading to a metal's reduced ability to resist further corrosion.
Step-by-step explanation:
Welding can cause oxidation, which is the chemical reaction between metal and substances such as oxygen in the environment. This reaction can degrade various properties of the metal, and in the context of the question provided, the correct answer is that it degrades corrosion resistance. Corrosion resistance is crucial because it prevents the metal from deteriorating quickly when exposed to the environment. Some metals like gold and platinum have high corrosion resistance naturally, while other metals such as aluminum develop a protective oxide layer that preserves the integrity of the metal beneath it.
For instance, aluminum reacts with oxygen to form a tightly bound aluminum oxide layer that protects the interior of the metal from further corrosion. However, not all forms of corrosion involve oxygen. For example, copper corrodes upon reacting with carbon dioxide and forms a green patina, which also serves as a protective layer against further corrosion.
Therefore, the correct answer to the student's question is that welding can cause oxidation which degrades corrosion resistance (c).