Which of the following metal parts shall be protected from corrosion?

Ferrous metal elbows, boxes, and raceways are susceptible to corrosion due to their iron content, making it essential to protect these components in order to maintain the integrity and longevity of electrical installations. In environments where moisture, chemicals, or other corrosive agents are present, unprotected ferrous metals can corrode quickly, leading to potential electrical hazards and equipment failure.

The NEC guidelines emphasize the need for corrosion protection to ensure a safe and reliable electrical system. Although aluminum, brass, and plastic components also have their own properties and handling requirements, they do not typically face the same level of corrosion risk as ferrous metals. For instance, while aluminum can naturally form a protective oxide layer, it may still require protective measures in certain environments, but it is less prone to rust than ferrous materials. Similarly, brass connectors and terminals, while having some resistance to corrosion, still need to be used properly in low-corrosion environments. Plastic conduit and fittings are not susceptible to rust at all, so they do not require corrosion protection.

Thus, recognizing that ferrous metals are particularly vulnerable to corrosion highlights the necessity of protective measures for these parts in compliance with safety standards and best practices outlined in the NEC.