Lead and Cadmium Distribution in Tubes of Galvanized Steel by Hot-Dip Used for Drinking Water Supply

The main objective of this work was to evaluate the presence of lead and cadmium in galvanized steel tubes by hot-dip used exclusively for drinking water supply. In this research, samples of galvanized tubes were removed from walls of residential buildings with 30 years of use. In the process of hot galvanizing, the manufacturing standards allow or for low cost conveniences, and the use of primary zinc ingot with 1.6% metallic impurities, such as lead and cadmium, is allowed, enabling the incorporation of these metals into the zinc coating deposited on the carbon steel. The associated corrosion of these tubes can release these toxic metals, contaminating the drinking water used by residents. The samples taken from the tubes were evaluated by a square-wave anodic stripping voltammetry technique, and the results for lead and cadmium suggested randomly distributed levels, indicating that the contents of these contaminants depend mainly on the quality of the added primary zinc and the operational conditions of the immersion bath. The metallographic evaluations performed on the samples of the galvanized tubes showed irregularities in thickness and even a lack of the zinc layer deposited on the carbon steel surface. These facts suggest that galvanized tubes should not be used for drinking water.