Degradation of monumental bronzes

Under the United States National Acid Precipitation Assessment Program a metallurgical and corrosion study has been made of sample of the 50 bronze replicas of the Hiker statue cast by the Gorham Foundry, Providence, Rhode Island, between 1906 and 1966. To study corrosion damage on a microscopic scale a technique was developed to take molds of selected features on the statue. The molds were examined by optical and scanning electron microscopy and surface profilometry. The overall approach has the potential for quantitatively monitoring the local corrosion at selected sites over a period of years and also characterizing the impact of conservation procedures. In a parallel research program, run-off samples were taken from selected Brigade Markers in a series of bronze tablets in the Gettysburg National Military Park; parallel rainwater samples were collected. Analysis for pH, metal content and various ion species in the run off yields information on the total rate of corrosion as a function of dry and wet precipitation.