What is the primary characteristic of localized corrosion?

Localized corrosion is marked by its occurrence in isolated areas rather than uniformly across entire surfaces. This type of corrosion typically develops in specific spots or regions, leading to significant damage concentrated in those areas while much of the surrounding material may remain unaffected. This characteristic is crucial in understanding how to manage and mitigate corrosion in various applications since it can lead to severe structural failures without being obvious until significant damage has occurred.

Uniform corrosion, in contrast, affects the entire surface evenly, making it easier to predict and manage. The other options, such as corrosion occurring only underwater or being prevalent only in acidic solutions, do not accurately capture the nature of localized corrosion, as it can happen in a variety of environments and conditions, not limited to specific situations.