The influence of carbon particles on the corrosion of iron in a humid,sulphur dioxide-containing atmosphere

Iron samples covered with a thin layer of activated carbon have been exposed to humid atmospheres at various relative humidities and with a various sulfur dioxide contents. Contrary to expectation the corrosion is initially faster at 55 and 65% relative humidity that at higher humidities. This phenomenon is attributed to adsorption of water vapour on activated charcoal, so that liquid films giving rise to corrosion can be formed at an earlier stage. After extended exposure, however, no accelerating effect can be attributed to the carbon particles.