Depth of severe corrosion?

• A. Over 0.010 inch
• B. Under 0.010 inch
• C. Exactly 0.010 inch
• D. 0.020 inch

Answer: (A)

Severe corrosion is defined by a depth that exceeds a specified threshold, here 0.010 inch (about 0.25 mm). When corrosion penetrates deeper than this, the metal loss becomes significant enough to reduce thickness and create stress concentrations, which can compromise structural integrity and fatigue life. That’s why any pit or area deeper than 0.010 inch is treated as severe, requiring more extensive repairs or replacement. If the depth is exactly 0.010 inch or shallower, it is typically not classified as severe and can often be addressed with standard corrosion removal and protective finishing. Measurements are taken after removing coatings to expose sound metal, using a depth micrometer or similar gauge to determine the exact depth.