Corrosion Coupons (weight loss measurements)

this is the simplest corrosion monitoring technique, which involves exposing a specimen of material (the coupon) to a process environment for a given duration, then removing the specimen for analysis. This usually means the measurement of weight loss; the corrosion rate can be calculated from the weight loss and the period the coupon was exposed.

Electrical Resistance Measurement

this technique measures the change in resistance of a corroding metal element exposed in a process stream. The corrosion of the element causes a decrease in its cross-sectional area and a resultant increase in electrical resistance from which the corrosion rate can be calculated.

Linear Polarization Resistance (LPR) Measurement

in simple terms the LPR technique involves the application of a small voltage to an electrode in solution. The current needed to maintain a specific potential shift is directly related to the corrosion on the surface of the electrode from which the corrosion rate can be derived instantaneously.

Galvanic/Potential Monitoring or Zero Resistance Ammetry (ZRA)

this is an electrochemical technique in which two electrodes of dissimilar metals are exposed to the process. The current generated due to the natural potential difference of the electrodes relates to the rate of corrosion that is occurring

Hydrogen Penetration Monitoring

in acidic process environments, hydrogen is generated in the corrosion reaction and can be absorbed by steel. This can lead to hydrogen induced failure. Probes are used to detect the amount of hydrogen permeating through the steel and this data can be used as an indication of corrosion rate.

Microbial or Biological Monitoring

Sulphate Reducing Bacteria (SRB) are anaerobic bacteria which consume sulphate from the process stream and generate corrosive sulphuric acid.