Abstract

Naval Research Laboratory (NRL)-Key West is a state-of-the-art testing facility for atmospheric and marine corrosion. The site naturally has elevated Ultraviolet (UV) intensity, similar to operational areas for the Navy. Recently, testing capabilities were expanded to include the ability to rinse samples with clear water (to mimic preventative maintenance washing), to shelter samples within a protective aircraft cover (to mimic preventative maintenance storage), and to spray samples with sea water (to increase the severity of the exposure). It is hypothesized that the Key West site can be tuned so as to mimic the exposure conditions of other sites of relevance to Navy operations.

A 2-Phase, multi-year site severity assessment was conducted to compare sixteen sites to Key West. Two standard Navy coatings (chrome and chrome-replacement) were exposed in addition to steel and silver corrosion coupons. This evaluation will update the relative ranking of these sites in terms of environmental severity index (ESI) and Total Corrosion Risk (TCR). Data presented will include steel mass loss, galvanostatic reduction of silver, and evaluation of the coated samples. In addition, select sites also received environmental dataloggers which will be compared against the exposure samples and nearby publicly available weather data in a follow up study. An understanding of how different local environments impact site-specific corrosion is developed and although many of the 16 test site environments are very different from the ambient conditions in Key West, there is an opportunity to simulate the environments of various bases at this one location. This can be achieved by altering the Key West environment through sea water application and sample sheltering or by adjusting the location and duration of exposure to match the base of interest.

Introduction

The exposure environment of an engineering material quite often has a large impact on how that material behaves over time. Environments are distinguished by differences in meteorological patterns, geography, salinity, Ultraviolet (UV) radiation, etc1-3. Thus, the degradation of various materials scales proportionately to the characteristics of the exposure site, with more severe sites leading to worse degradation. Developing an understanding of how the local environment impacts the corrosion rates of metals and the deterioration of anti-corrosion coatings is critical for informing asset maintenance schedules and lifetime predictions4.

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