Agar as an analogue for soil in corrosion studies: Where to next?

Semi-solid agar has been developed as an analogue for soil to be used in corrosion studies, especially those involving microbiologically influenced corrosion (MIC). This is in response to the recognition of major short comings of the traditionally utilized electrolytes for soil corrosion. Soil corrosion is typically studied in solution systems which are unable to replicate the physical characteristics of soils which are intrinsic both to the corrosion of metals in soil and, when studying MIC, the movement of microbes through soil. The development process has focused on the use of semi-solid agar as an electrolyte. The stable electrochemical region of semi-solid agar and the effect of nutrients on the system have been determined and a series of experiments determining the effect of Pseudomonas fluorescens on carbon steel in the system conducted. The studies have shown that a correlation exists between the semi solid agar system and clay based soils in terms of the properties and resultant corrosion behaviour of carbon steel in contact with the system. This paper reviews the research to date and then considers the next steps in the system development. It discusses the system in relation to the wider soil corrosion literature and suggests applications where it would be advantageous to use semi solid agar or derivatives of the system.