Which statement about pitting factor is true?

• A. It is the ratio of the deepest pit depth to the total surface area affected.
• B. It measures the number of pits per area.
• C. It indicates uniform corrosion rate.
• D. It is the ratio of the deepest pit depth to the average metal loss; higher values indicate more severe pitting.

Answer: (D)

Pitting factor measures how localized the corrosion is by comparing the deepest pit depth to the average depth of the pits (often described as the average metal loss due to pitting). If the deepest pit is much deeper than the typical pit, the pitting is highly localized and the pitting factor is large; if all pits are similar in depth, the factor is around 1, indicating more uniform attack. This is why the correct statement says it is the ratio of the deepest pit depth to the average metal loss, and that higher values indicate more severe pitting. It doesn’t involve pit density or surface area, and it doesn’t directly indicate the overall uniform corrosion rate.