Corrosion behavior of zinc in simulated concrete pore solutions

Abstract

The corrosion behaviour of zinc samples has been studied in simulated concrete pore solution (saturated Ca(OH)i solution) that contained 50% calcium hydroxide, Ca(OH)2 and 50% seawater (NaCl) for beaker 1. Whereas in beaker 2, the solution used was 50% calcium hydroxide, Ca(OH)2 and 50% distilled water (H20). These experiments were done at room temperature condition. The beneficial aspects of zinc samples were revealed from the experiments conducted. Weight loss of zinc samples as well as their surface morphology in the presence of calcium hydroxide, Ca(OH)i, seawater (NaCl), and distilled water (H20) were investigated. Weight loss experiment involving immersion of the samples in the solution provided was conducted for 49 days or equivalent to 7 weeks. The effects of dissolved oxygen in environmental condition on all samples in both solutions were also investigated. The corrosion products and the microstructure on the zinc samples were characterized using Scanning Electron Microscope and Energy• Dispersed X-ray Spectroscopy (SEM-EDS). The plots of graphs obtained showed that the weight losses of both samples in both beaker increases with the immersion of time. The results showed that the samples in beaker 1 have higher value of weight loss with the same duration of immersion time as compared to that of samples in beaker 2. The presence of more oxygen in beaker 1 with the usage of seawater (Na Cl) with the presence of organisms contributes to the dissolution of zinc, hence increasing the weight loss. The corrosion rates in both solutions and both beakers decreased with the increasing of time due to the contamination of the seawater environment by corrosion deposits that weakened the water and at the same time reduced the chemical reactivity that supposed to occur. Corrosion process in deep seawaters occurs under much specified conditions and is characterized mainly by high chloride contents, the presence of C02 and H2S and also micro organism. In the micrographs, flakes are clearly seen which prove the presence of corrosion products like metal hydroxides and its oxides. From the analysis, it shows that the ferum (corrosion) exists in beaker 2 is less compared to beaker 1. The existence of micro organisms from the usage of seawater as part of solution in beaker 1 contributes to the corrosion developments in beaker 1.