Rapid determination of the corrosion properties of lead alloys

摘要

Lead has been used for at least 5,500 years. Nowadays, properties like a high corrosionrnresistance and its malleability, durability and flexibility still make lead unique for a number ofrnapplications such as the extensive use of lead sheets in the building industry.rnTo improve specific application properties, lead is alloyed with various elements. The leadrnalloys used for buildings have an attractive appearance, low production costs and a low runoffrnrate. However, due to environmental and health concerns it is desired to further reduce thernrunoff from buildings.rnTo investigate the long-term corrosion properties, lead sheets of experimental alloys have tornbe exposed outdoors for a number of years. Rainwater from the exposed samples has to berncollected and analysed for the contents of lead and its main alloying elements. From thesernresults, the runoff rate can be calculated.rnIn the current work, the outdoor performance new lead alloys is compared to the results ofrnelectrochemical measurements performed in the laboratory. For the latter, electrochemicalrncells were mounted on duplicates of the alloys. Concentrated (artificial) rainwater served asrnelectrolyte. The corrosion potential and polarisation resistance was monitored until a stablernvalue was reached.rnUp to now, four alloys and pure lead have been measured, and the results of thernelectrochemical measurements can be related to the runoff rate. The alloys with a lowrncorrosion resistance also show a high runoff rate when exposed outdoor. The alloys thatrndevelop a high corrosion resistance by building up a protective layer show a low runoff rate.rnIt is shown that results of electrochemical measurements appear to be helpful for the rapidrndetermination of the corrosion and runoff properties of lead alloys. Outdoor exposure of leadrnalloys requires years to determine the long-term corrosion properties, while electrochemicalrnmeasurements allow a ranking of these properties within weeks.