Comparative study of the corrosion behavior of three alpha brass alloys used in potable water distribution equipment in aggressive soil using electrochemical measurements

Abstract

Cu–Zn (brass) materials are widely used in drinking water equipment, including valves, taps, and fittings. However, this brass suffers significant corrosion when buried in aggressive soil. The aim of this study is to investigate the corrosion resistance of three α-brasses (Br1, Br2 and Br3) buried in aggressive soil of the MNASRA region, located in the province of Kenitra, north-west Morocco. This study was carried out by means of potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and open circuit potential (OCP) measurements. A pilot plant was designed to simulate the environment in which the materials were used, and the same materials were buried on the site where they were used for a period of two years. The results show an increase in icorr from 3050 at 24 h to 5400 μA cm−2 at 2016 h for Br3 and from 1330 to 2550 μA cm−2 for Br2. However, Rp decreases from 181.9 to 2.8 kΩ cm2 for Br3 and from 489.9 to 85.2 kΩ cm2 for Br2, indicating that the Br3 and Br2 alloys have undergone significant corrosion in the aggressive soil respectively. Where as a decrease in icorr from 1.280 at 24 h to 0.430 μA cm−2 at 2016 h for Br1. Nevertheless, Rp increased from 192.1 to 881.7 kΩ cm2 indicating an improvement in corrosion resistance due to the formation of a denser protective film on its surface. Moreover, the results show that the presence of a high phosphorus (P) and aluminum (Al) content with a lower percentage of iron (Fe) has a beneficial effect and leads to good corrosion resistance. These results are in agreement with the SEM/EDS and XRD analyses, as well as with the results obtained on-site after two years of immersion by SEM and OP analyses.