Red Seal Ironworker (Reinforcing) Practice Exam 2025 - Free Reinforcing Ironworker Practice Questions and Study Guide

The primary cause of corrosion in reinforcing steel is closely related to exposure to moisture and chlorides. When reinforcing steel is embedded in concrete, it is generally protected from corrosion by the alkaline environment created by the cement. However, when moisture infiltrates the concrete, especially when combined with chlorides (such as those found in de-icing salts), it can lead to the breakdown of the protective oxide layer on the steel. This results in rust formation, which expands and can cause cracking and spalling of the concrete.

The presence of moisture acts as an electrolyte that facilitates the electrochemical reactions necessary for corrosion to occur, while chlorides can significantly accelerate this process by weakening the protective barrier around the steel. Therefore, the combination of moisture and chlorides is a well-known and primary trigger for the corrosion process in reinforcing steel within concrete structures.