A Field Survey of Soil Corrosivity Level of Kaduna Metropolitan Area through Electrical Resistivity Method

Soil resistivity-corrosivity is basic in the analysis of corrosion problems and design of corrective measures. It can differ widely at different geographical areas. This paper focuses on soil corrosivity level as it concerns critical underground engineering structures which in the past few decades have continued to be inevitably installed or erected as some technological means of development in Kaduna-a top populous, administrative, industrial, and military garrison city in Nigeria. The survey was conducted at 310 different underground locations up to 4.5m-depth during annual period of peak rainfall (August to October 2014) in the area through the ASTM G57-06 standard test method for field measurement of soil resistivity. Dispersion analysis of the obtained information was carried out using Microsoft Excel statistical facility. The analysis indicates that within the survey depths, the soil resistivity of the area is generally different at each location and increases downwards. The resistivity varies within the extremes of 31.9 Ohm-m at the depth of 0.5m to152.9 Ohm-m at the depth of 4.5m with overall mean value of 72.13481 Ohm-m, standard deviation of 33.78109 Ohm-m and coefficient of variation 46.83%. Translated into corrosivity, the analysis represent a stochastically variable soil corrosivity spectrum that is mildly corrosive on average and generally varies downwards underground from aggressive at depths of less than about 0.5m to slightly corrosive around 4.5m. The paper intends to provide some supplementary, readily available and applicable predictive information for strategic corrosion control in the area.