Silica effects on corrosion of iron pipes under anaerobic conditions

Silica is used as a corrosion inhibitor in the water treatment industry and is also a naturally occurring water constituent. To examine the effects of silica on iron pipe corrosion under anaerobic conditions, two sets of preliminary experiments were performed using a stagnant pipe rig. In Phase I, four different silica levels were tested in deoxygenated water. In Phase II, two silica levels were tested in both oxygenated and deoxygenated waters.; During five months of experiments, silica did not impact the total iron released into the pipe water. However, higher silica levels caused more ferrous iron and soluble iron to be released to the water. The pipes with higher silica also had more scale built up on the pipe surface, and X-ray diffraction showed that the scale was more amorphous. These experiments indicated that silica did not prevent iron pipe corrosion and even had adverse effects under these conditions.