PCS Corrosion Science and Prevention Flashcards

According to NACE/AMPP standards, what maximum soluble salt level (expressed as equivalent NaCl) is generally acceptable on steel before immersion-service coating application?

Answer: 20 µg/cm²

Industry practice and many specifications limit soluble salt contamination to 20 µg/cm² equivalent NaCl or less on steel destined for immersion or severe service coating.

What type of corrosion results from cyclic loading of a metal structure in a corrosive environment, leading to crack initiation at lower stress levels than in air?

Answer: Corrosion fatigue

Corrosion fatigue is the synergistic effect of cyclic mechanical stress combined with a corrosive environment, causing crack initiation and propagation at stresses well below the normal fatigue limit.

In cathodic protection (CP) systems, what is the minimum protective potential (Cu/CuSO4 reference) for buried or submerged steel as specified by NACE SP0169?

Answer: -0.85 V

NACE SP0169 specifies that a minimum protective potential of -0.85 V measured with a Cu/CuSO4 reference electrode indicates cathodic protection of buried or submerged steel.

Which atmospheric category in ISO 9223 represents the most severe corrosion environment (offshore/tropical industrial)?

Answer: CX

ISO 9223 category CX (formerly C5-M extreme marine) designates the most corrosive atmospheric environment, typically found at offshore platforms or tropical industrial locations.

What is the corrosion mechanism known as 'undercutting' in relation to coated steel?

Answer: Corrosion spreading laterally beneath the coating from a defect

Undercutting (or filiform creep) is lateral corrosion migration beneath the coating film from a defect such as a scratch or holiday, progressively delaminating the coating from the substrate.

Which standardized test method subjects coated steel panels to a continuous salt fog to evaluate coating corrosion resistance?

Answer: ASTM B117

ASTM B117 is the Standard Practice for Operating Salt Spray (Fog) Apparatus, widely used to evaluate coating corrosion resistance under accelerated salt fog exposure.