Marine & Transportion
The marine environment presents a unique set of challenges for engineered structures and components. The relentless combination of seawater, waves, marine organisms, and varying operational conditions can lead to various failure modes. Failure analysis in marine contexts aims to dissect these failures, enabling engineers and scientists to design more resilient marine systems and prevent future incidents.
Example One: Weld Deterioration
Sea air can be bracing and refreshing, but the combination of moist air and chloride can lead to severe atmospheric corrosion.
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The images below show the sequence of deterioration of a weld on a the handrail of a coastal footbridge Most of the hand rail facing the sea remained in good condition, protected by a galvanized coating of zinc.
Unfortunately, the protective zinc coating that was removed by the heat of welding, was not replaced.
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This exposed the steel weldment to the sea air and complete destruction of the weld by marine corrosion over a matter of three years.
Example Two: Marine Corrosion
A E-field perimeter protection system surrounding an important plant facility on the coast suffered severe corrosion of the cast aluminum housings.
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A failure analysis found that casting had been incorrectly made from ASTM Specification B85 grade 380, rather than the grade 360 specified on the drawing.
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The key difference in the alloy designations is that grade 380 contains deliberate additions of copper and zinc, both elements of which, severely lower the corrosion resistance of the alloy.
Galvanic corrosion of the aluminum matrix around bright copper precipitates.
