Corrosion rate measurement of galvanised fire services in drinking water

摘要

OneSteel Market Mills have commissioned Hunter Water Australia to carry out a laboratory study to measure the corrosion rate of galvanised steel pipes in a limited range of water compositions and conditions of aeration. The work has established that electrochemical techniques for the measurement of corrosion rates to a reasonable degree of accuracy are currently available. Results indicate that the corrosion rate, and hence the life expectancy of galvanised tube, is very dependent on the physical aeration conditions of the water. Galvanised steel in fully deaerated conditions can be expected to experience corrosion rates as low as 0.5-1.0 microns per year, meaning a galvanised life cycle considerably in excess of 50 years can be confidently expected. However, aeration and stirring corresponding to the continual use of a galvanised service will lessen the life expectancy to as little as 2 years. The corrosive influence of dissolved carbon dioxide will further lessen the life expectancy to a few months. These results provide an experimental framework to assess the long-term rig trials currently being conducted by OneSteel, as well as providing a basis for more detailed study if this is required.