Protective ability of lead corrosion products in indoor atmosphere with acetic acid vapours

Lead corrosion products can undergo certain changes over the time in terms of composition. How these changes affect the corrosion of the underlying lead is an important question for protection of historical lead artefacts. In this work, we focus on characterization of changes in composition of lead corrosion products and how the composition affects corrosion of the lead substrate. Prepared model corrosion products on lead coupons were exposed to air at different relative humidity and concertation of acetic acid vapours. Composition of the corrosion products was analysed by XRD and corrosion rate was calculated from gravimetric data. Measurement of polarization resistance was implemented to get more insight into the protective ability of formate corrosion products. With lead formate covering the surface, the corrosion rate of lead coupons was minimal even in humid air with 400 ppb of acetic acid vapours. Acetic acid was however able to alter lead carbonate corrosion products resulting in increased corrosion rate.