API 571 Certification (Corrosion & Materials) Practice Test

Pitting corrosion is a localized form of corrosion that leads to the formation of small pits or cavities in a material, often metal. One of the primary factors that significantly increases the risk of pitting corrosion is the presence of chloride ions. Chloride ions, commonly found in saltwater and many industrial environments, can break down the protective oxide layer on metals, particularly stainless steels and other alloys. This breakdown allows for localized corrosion to occur, leading to the formation of pits.

When chloride concentrations are increased, the likelihood of pitting corrosion rises due to the ability of these ions to disrupt the passive film that protects the metal surface. The pits that form can penetrate the material rapidly, often leading to failure before any significant uniform corrosion is detected. Understanding the role of chloride ions in pitting corrosion is crucial for assessing material performance in corrosive environments and choosing appropriate materials and protective measures accordingly.