API 571 Certification (Corrosion & Materials) 2025 – 400 Free Practice Questions to Pass the Exam

Pitting corrosion is specifically characterized by the formation of small, localized areas of corrosion, known as pits, on a material's surface. This type of corrosion often occurs in metals that have protective oxide layers, such as stainless steel. When these protective layers become damaged, localized corrosion can initiate, leading to the development of pits. This can lead to significant material degradation over time because pits can penetrate deeper than the surrounding areas, often resulting in failure of structural integrity long before uniform corrosion would be evident.

Uniform corrosion, on the other hand, affects the entire surface of the material uniformly, which results in a more consistent and predictable loss of thickness, but does not create pits. Crevice corrosion occurs in confined spaces where stagnant solutions can occur, leading to localized corrosion but is different in mechanism and characteristics from pitting. Galvanic corrosion arises when two dissimilar metals are in electrical contact in an electrolyte, leading to corrosion of one metal, but it does not necessarily involve the formation of pits as a primary characteristic. Thus, pitting corrosion uniquely describes the phenomenon where pits form, making it the most appropriate answer to the question.