The Corrosion Behavior And Mechanism Of Metallic Cultural Relics Exposed To Ozone

Ozone, as an oxidant, has strong oxidation and corrosion effect. Ozone not only can result in degradation of organic cultural relics such as textile, leather, photo and pigment, but also can damage kinds of metallic cultural relics in various degrees, for example, ozone can accelerate the oxidation of silver and ferrum and the sulfuration of silver and copper. Serious injury from ozone to cultural relics has attracted wide attention of domestic and international experts and scholars.In this study the quartz crystal microbalance(QCM), scanning kelvin probe(SKP), scanning electron microscope(SEM), raman spectroscopy and x-ray photoelectron emission microscopy(XPS) were used for investigation of the corrosion behavior and mechanism of typical metallic cultural relics when exposed to ozone environment. Through monitoring the frequency change of silver-electrodeposited and copper-electrodeposited quartz crystals at different ozone concentrations, different temperatures and different relative humidities, the corrosion kinetic curves were obtained. According to these curves, the corrosion rates and other related parameters were calculated. Meanwhile, combining the metal surface morphology and the change of surface potential distribution, the corrosion mechanism involved was put forward. Analysis of main constituent of corrosion product on metal surface further proved the previous corrosion mechanism. At last by fitting the dose-response function, the relationship between corrosion rate and environmental impacting factors was initially built.The result obtained from QCM showed that the ozone concentration and the temperature are very important environmental parameters influenced silver and copper corrosion. With the increase of ozone concentration and temperature, the extent of corrosion was aggravated. Silver has a less sensitive to relative humidity.The analysis of raman spectroscopy and XPS indicated that after exposed to 5μg/L ozone for 1 d and 3d, Ag2O was formed on silver surface and an outer corrosion product layer containing CuO was formed over an inner layer that contained Cu2O on copper surface. Copper suffered more serious corrosion with the exposure time when exposed to ozone than natural air.