ATO Corrosion Practice Exam

Assessing corrosion severity comes from combining several indicators of damage rather than relying on a single sign. Discoloration shows that the metal surface has changed, indicating corrosion activity underway. Pitting depth provides a direct measure of how deep the corrosion has penetrated, which is crucial for assessing structural risk. Blisters reveal coating failure and underlying corrosion, meaning protection is no longer preventing attack. Scaling indicates the protective layer has been removed in areas, exposing fresh metal to the environment and allowing ongoing corrosion. Together, these signals give a fuller, more accurate picture of how severe the corrosion is. Relying on color alone misses depth and coating issues, so the most complete assessment uses all four features: discoloration, pitting depth, blisters, and scaling.