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Accelerated Field Exposure using Seawater Spray: A Comparison to Traditional Atmospheric Test Methods

The objective was to compare the effect on corrosion of different field exposure conditions: atmospheric exposure in a medium chloride environment, atmospheric exposure with periodic seawater spray, cyclic alternate immersion, and a typical accelerated atmospheric testing protocol (GM 9540).

Product Number: 51317--9335-SG
ISBN: 9335 2017 CP
Author: Derek Horton
Publication Date: 2017
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Often the most severe maritime environmental degradation for ships occurs just above the waterline within the splash zone where periodic wet-dry cycles accelerate corrosion. Similarly increased corrosion also occurs at coastal areas where nearby wave action generates more sea-spray aerosols. These areas are subjected to typical degradation through atmospheric deposition and stressors such as UV light but also have an increased time of wetness (ToW) and higher chloride deposition rate compared to atmospheric exposure alone. It has been seen previously that elevated ToW and chloride loading are correlated to higher corrosion rates of various materials.The objective of this series of testing was to compare the effect of different field exposure conditions on corrosion performance: atmospheric exposure in a medium chloride environment atmospheric exposure with periodic seawater spray cyclic alternate immersion and a typical accelerated atmospheric testing protocol (GM 9540). Test materials included copper alloys silver and carbon steel. Oxide analysis was performed using electrochemical impedance and coulometric reduction. These techniques were used in conjunction with microscopy profilometry and other characterization tools to determine the change in surface state and corrosion rates of the exposed materials as a result of the different field exposures.

Key words: Atmospheric Corrosion, sea spray, alternate immersion, Ag, Cu

 

 

Often the most severe maritime environmental degradation for ships occurs just above the waterline within the splash zone where periodic wet-dry cycles accelerate corrosion. Similarly increased corrosion also occurs at coastal areas where nearby wave action generates more sea-spray aerosols. These areas are subjected to typical degradation through atmospheric deposition and stressors such as UV light but also have an increased time of wetness (ToW) and higher chloride deposition rate compared to atmospheric exposure alone. It has been seen previously that elevated ToW and chloride loading are correlated to higher corrosion rates of various materials.The objective of this series of testing was to compare the effect of different field exposure conditions on corrosion performance: atmospheric exposure in a medium chloride environment atmospheric exposure with periodic seawater spray cyclic alternate immersion and a typical accelerated atmospheric testing protocol (GM 9540). Test materials included copper alloys silver and carbon steel. Oxide analysis was performed using electrochemical impedance and coulometric reduction. These techniques were used in conjunction with microscopy profilometry and other characterization tools to determine the change in surface state and corrosion rates of the exposed materials as a result of the different field exposures.

Key words: Atmospheric Corrosion, sea spray, alternate immersion, Ag, Cu

 

 

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