Soil Physico-Chemical Charateristics and Metalic Corrosion in Parts of The Niger Delta

Irunkwor T. C, Ngerebara O. D

Soil physico-chemical parameters such as pH, organic matter, chloride and sulphate contents were investigated to assess their effect on buried metallic pipes for a proposed gas processing plant facility at Ovade-Ogharefe, Delta State, Nigeria. Ten sampling points along the pipeline route were investigated. Thus, a total of 10 borings each to a depth of 10.0m were drilled along the pipeline route using the Shell-and-Auger Percussion Rig to collect subsurface soil samples for laboratory analyses for physico-chemical characteristics. Soil pH was determined in-situ electronically using the glass electrode method with a standard calibrated pH meter. On the average, the soil is sandy clayey in nature and the results of the parameters tested are as follows: pH (5.2-7.5), chloride (8.9-85.4ppm), sulphate (126.3-266.5ppm) and organic matter content (0.41-0.42%). The low pH values of 4.2, 5.2, 5.3 and 5.5 as well as the high sulphate contents above permissible limit respectively at locations BH7, BH8, BH9 and BH10 implies that the soil is acidic and deleterious to buried metallic pipes which is  characteristic of clayey soils. It is recommended that the metallic pipes along the pipeline route be buried within the depth of 2.0 to 3.0m because that is the zone or layer of high pH, low chloride and low sulphate contents. However, the impressed current cathodic protection method is therefore recommended to minimize corrosion impact on the proposed gas pipeline.