What are common visual indicators of pitting corrosion?

What are common visual indicators of pitting corrosion?

• A. Uniform dulling
• B. White powder on surface or small pockmarks
• C. General brightening
• D. No signs

Answer: (B)

Pitting corrosion shows up as localized, tiny pits rather than a uniform change across the surface. When the protective oxide film on the metal is damaged at discrete spots, small pits form and can look like pockmarks. In aircraft aluminum alloys, these pits are often accompanied by a white, powdery corrosion product (white rust) from aluminum hydroxide forming in damp, chloride-containing environments. So the hallmark visual signs are white powder on the surface together with small pockmarks. Uniform dulling or general brightening would point to different types of surface change, not localized pits, and no signs would mean no visible corrosion at all.

Pitting corrosion shows up as localized, tiny pits rather than a uniform change across the surface. When the protective oxide film on the metal is damaged at discrete spots, small pits form and can look like pockmarks. In aircraft aluminum alloys, these pits are often accompanied by a white, powdery corrosion product (white rust) from aluminum hydroxide forming in damp, chloride-containing environments. So the hallmark visual signs are white powder on the surface together with small pockmarks. Uniform dulling or general brightening would point to different types of surface change, not localized pits, and no signs would mean no visible corrosion at all.