Laserfiche WebLink
LAW/CRANDALL, INC.June 26,1997 <br />MJS&A #97192 Page 2 <br />SOIL CORROSIVITY <br />A major factor in determining soil corrosivity is electrical resistivity. The electrical resistivity of a <br />soil is a measure of its resistance to the flow of electrical current. Corrosion of buried metal is an <br />electrochemical process in which the amount of metal loss due to corrosion is directly proportional <br />to the flow of electrical current (DC) from the metal into the soil. Corrosion currents, following <br />Ohm's Law, are inversely proportional to soil resistivity. Lower electrical resistivities result from <br />higher moisture and chemical contents and indicate corrosive soil. <br />A correlation between electrical resistivity and corrosivity toward ferrous metals is: <br />Soil Resistivity <br />in ohm-centimeters Corrosivity Category <br />over 10,000 mildly corrosive <br />2,000 to 10,000 moderately corrosive <br />1,000 to 2,000 corrosive <br />below 1,000 severely corrosive <br />Other soil characteristics that may influence corrosivity towards metals are pH, chemical content, <br />soil types, aeration, anaerobic conditions, and site drainage. <br />Electrical resistivities were in mildly and moderately corrosive categories with as-received <br />moisture. When saturated, both resistivities dropped into the moderately corrosive category. <br />Soil pH values were 6.4 and 6.5. These values are slightly acidic and do not particularly increase <br />soil corrosivity. <br />The chemical content of the samples was low. <br />Tests were not made for sulfide or negative oxidation-reduction (redox) potentials because they <br />would not exist in these aerated samples. <br />This soil is classified as moderately corrosive to ferrous metals.