Tables (2) through (9) show the corrosion rates of the alloys used at different exposure sites and under different exposure time. The results show that the carbon steel G1020 has the maximum corrosion rate in all three locations whilst the inconel alloy 625 shows the lowest corrosion rate. Under fully immersed condition, there is a decrease in corrosion rates with increasing of exposure time for all the test alloys. The reason for this phenomenon may differ from alloy to alloy mainly depending on chemical composition of the exposed alloy. For carbon steel, the corrosion product will be built up on the surface which would reduce the mass transfer of oxygen and other agents to the metal surface resulting in the reduction of the kinetic of the cathodic reactions. Therefore, the increase in the corrosion product thickness will decrease the corrosion rate. The corrosion product on the copper nickel alloys surface has the ability to protect these alloys. This corrosion film is usually quickly formed on the alloy surface but it takes considerably long time to reach a steady state. This corrosion film is usually enriched by iron oxide and nickel oxide and therefore, the corrosion rate of copper based alloys may be effected by iron content in the alloy composition and/or ferrous ions in water stream. The decease in corrosion rate of stainless steel with time could be attributed to the thickening of passive film on the alloy surface.