Metal Samples MS2500L, Operator'S Manual

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5. Suspended Solids
An increase in suspended solids levels will accelerate corrosion rates. These solids
include any inorganic or organic contaminants present in the water. Examples of
these contaminants include clay, sand, silt or biomass.
Some specific contaminants can interfere with the Linear Polarization corrosion rate
measurement, among these are iron sulfide, and hydrocarbons.
Iron sulfide, in the form frequently encountered in some applications, is electroni-
cally conductive. Since the Linear Polarization Technique assumes ionic conductiv-
ity between the electrodes, this interferes with the measurements. When significant
amounts of FeS are present in the system, its interference exhibits itself as rapidly
increasing corrosion rates until the maximum full scale (or unreasonably high) level
is reached.
In the opposite way, hydrocarbon contamination of Linear Polarization electrodes
will effect the readings. Usually, hydrocarbon “coating” of the electrodes isolates
them from the electrolyte and from electrical communication with each other. This
results in very low corrosion rate readings.