Statistical Analysis of Environmental Parameters: Correlations between Time of Wetness and Corrosion Severity

The cost of corrosion remains a sizeable budgetary concern across the Department of Defense. Naval aviation and material are particularly impacted due to their mission profiles. As such, ongoing research into the prediction and prevention of corrosion within the fleet is necessary. Environmental exposure sites provide the closest correlation between corrosion degradation and damage experienced in-service; however, testing is time-consuming, not widely accessible, and provides cumulative data only. Consequently, an in-depth understanding of the naval operating environment is crucial both in the prediction and mitigation of corrosion damage. We present results of dynamic environmental monitoring on-board a naval ship, and its correlation to corrosion degradation. A device measuring solution resistance (SR) across a gold interdigitated electrode, surface temperature (surface T), and relative humidity (RH), dynamically monitors environmental parameters over a period of nine months. Rigorous statistical analysis is used to analyze SR data and correlate those measurements to mass loss experienced by witness coupons exposed to the same environment. Data are then used to determine probabilities of wetness (and semiwetness) as a function of absolute humidity (H); results are compared to those predicted by “ISO 9223:2012 Corrosion of metals and alloys–Corrosivity of atmospheres–Classification, determination, and estimation.” Finally, corrosion action zones (CAZs) are constructed and delineate conditions in which wetness and semiwetness are likely.