Red Seal Boilermaker Practice Exam

What does pitting corrosion refer to?

1. A uniform corrosion covering the entire surface

2. A type of corrosion that affects only stainless steel

3. Localized corrosion that creates small holes in a material

4. A method to enhance surface strength of metals

The correct answer is: Localized corrosion that creates small holes in a material

Pitting corrosion is a specific form of localized corrosion that results in the formation of small holes, or "pits," in the material, particularly metals. This type of corrosion occurs when small areas of a metal surface become anodic (corroding) while the surrounding areas are cathodic (protected). Pitting is often initiated by environmental factors, such as the presence of chloride ions, which can infiltrate protective oxide layers on materials like stainless steel, aluminum, and other metals. Unlike uniform corrosion that affects the entire surface of the metal evenly, pitting is characterized by its localized nature, which can lead to significant structural weaknesses even when the overall material appears intact. Understanding pitting corrosion is vital for boilermakers, as it can compromise the integrity of boiler systems, leading to failures if not addressed. This localized attack does not require the metal to be particularly susceptible to corrosion as a whole; rather, it indicates that specific conditions have allowed for this more severe form of damage.