Effect of Phosphate Inhibitors on the Formation of Lead Phosphate/Carbonate Nanorods, Microrods, and Dendritic Structures

Abstract

There are several factors which influence the corrosion rate of lead, which in turn morphs into different crystal shapes and sizes. Some of the important factors are alkalinity, pH, calcium, orthophosphate, and silica. Low to moderate alkalinity decreases corrosion rates, while higher alkalinities have a tendency to increase the corrosion rates of lead. This work describes the effect of orthophosphate inhibitor and pH on the formation of different structures of lead phosphate/carbonate nanorods, nanobelts, microrods, and dendritic structures. The experiments were carried out at different pHs both with and without orthophosphate inhibitor under laboratory conditions, which were intended to represent actual drinking water distribution system (DWDS) conditions. The surface morphology and crystal structure of the different crystals were obtained using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), transmission electron microscopy (TEM), and selected area diffraction pattern (SAED). The phase identification was done using powder X-ray diffraction (PXRD). With the increase in pH from 6.5 to 8.5, the formation of uniform thickness coating of phosphate containing minerals was observed, which was in contrast to the different crystal growth under low pH conditions. The XRD patterns indicate that the surface solids contain a mixture of many phases.