Development of chloropyromorphite coatings for lead water pipes

Formation of inorganic barrier coatings on lead water pipes might be an attractive option for water companies wishing to reduce lead levels in drinking water. This paper concerns the treatment of such pipes with aqueous solutions containing oxidant together with sources of phosphate and chloride to generate coatings of the highly insoluble lead mineral chloropyromorphite, Pb5(PO4)3Cl by simultaneous oxidation and precipitation. SEM, TEM, XRD and overnight leaching tests were used to characterise the structure and performance of the coatings. The impact of the choice of oxidant on the coating morphology and barrier properties is explored. Strategies for further refinement of the coatings via improved process control and morphological modification are discussed.