Two-Year Atmospheric Corrosion and Accelerated Corrosion Test: A Comparative Study

摘要

The accelerated corrosion of pure silver (UNS P07020), three aerospace aluminum alloys (UNS A92024, UNS A96061 and UNS A97075), pure copper (UNS C10100) and carbon steel (UNS G10100) in a standard ASTM B117 (5wt% NaCl solution at 95 ℉ and 95% RH) salt spray test as well as a modified ASTM B117 salt spray test that included ozone (100 and 800 ppb) and ultraviolet A (0.1 and 0.85 W/m~2) were investigated and compared to the corrosion observed on identical samples exposed over a two year period in the field at eight geographic locations. The effects of environmental and climate factors on the atmospheric corrosion of both the field and chamber exposed samples were determined with gravimetric measurements, coulometric reduction, and chemical composition and morphology using scanning electron microscopy - energy dispersive spectroscopy. Aluminum alloys (UNS A92024 and UNS A97075) exposed at Daytona Beach (FL) exhibited the highest mass loss while those exposed at the Kirtland Air Force Base (NM) site exhibited the lowest mass loss. Silver coupons (UNS P07020) exposed at Daytona Beach (FL) also exhibited the highest AgCl film thickness values while silver coupons (UNS P07020) at the Kirtland Air Force Base (NM) exposure site exhibited the lowest film thickness values. The corrosion rates of the samples exposed in the modified B117 corrosion chamber under ultraviolet A and ozone conditions were much higher than those of the field exposures as well as the standard B117 salt spray test.