Corrosion of 1010 carbon steel exposed to semi-solid agar

Corrosion of steel potable water pipes buried underground is one of their key means of failure, though it is often trivialised. General corrosion of buried pipes is minimal and is readily counteracted. In contrast, localised corrosion such as pitting is the primary means of pipes failing. A leading cause of pitting is the action of microbes at the steel/soil interface. This is both difficult to predict and prevent and can lead to leaks and ultimately to failure by bursts. These can be expensive to locate and repair. In order to study localised corrosion influenced by microbes at the steel/soil interface, a system is being developed which utilises microbiologically graded agar for electrochemical studies. Earlier work focussed on solid agar and the electrochemical performance of 1010 carbon steel exposed to agar and sodium chloride. This paper investigates the electrochemical performance of the same steel exposed to semi solid agar made with a lower concentration of gelling agent and how this compares to that of steel exposed to solid agar. Electrochemical behaviour was monitored with both potentiodynamic scans and potential hold measurements. Following electrochemical testing the surface of the steel samples were examined with optical and scanning electron microscopy. It is hypothesised that this system is more representative of a soil environment than solution based systems and is more readily controlled than soil samples for fundamental studies of MIC.