Corrosion inhibition of carbon steel in various water types by zinc gluconate

The effect of zinc gluconate on the corrosion inhibition of carbon steel DIN RSt 37-2 in various water types has been evaluated using Tafel polarization and scanning electron microscopy techniques. Experiments were performed using 6 types of water, namely, soft tap water from Dubrovnik region, hard tap water from Zagreb region, 3.5 % sodium chloride solution, sea water from Dubrovnik region, biologically inert sea water from Dubrovnik region and demineralized water. The concentration of zinc gluconate varied from 0.1 to 3 gl-1. The results show that substantial corrosion inhibition using zinc gluconate can be obtained with low concentrations in tap waters along with demineralized water and with moderate concentrations in 3.5 % sodium chloride solution and sea waters. EDX analysis confirmed the presence of zinc ions which are incorporated in the protective layer of carbon steel specimen. The corrosion inhibition is predominately obtained by anodic mechanism.