Comparison of the early stages of corrosion of copper and iron investigated by in situ TM-AFM

Abstract

Tapping mode atomic force microscopy (TM-AFM) was used for the investigation of the early stages of atmospheric corrosion of pure copper and pure iron. The information obtained by this method is the change of the topography of the sample surfaces with emphasis on the shape and lateral distribution of the corrosion products grown within the first 1300 min of weathering. Investigations were carried out in synthetic air at 80 and 90% relative humidity (RH) with additions of 250 ppb SO 2 and 250 ppb NO 2. On a polished copper surface the growth of corrosion products could be observed already at 80% RH and 250 ppb SO 2, whereas an iron surface had to be exposed to 90% RH with 250 ppb SO 2 and 250 ppb NO 2 to produce detectable changes on the surface.