Corrosion monitoring in the oil refining industry: A review

The aim of this work is to review and analyse corrosion monitoring methods existing in the oil refining industry, and to give examples of their use in the oil refineries' units. Corrosion monitoring (CM) is an integral part of anti-corrosion management in the oil refining industry. The more refineries spend on CM, the less corrosion damage will occur, resulting in less corrosion loss. Our estimation showed that some refineries spend about 3.75% of corrosion costs (direct and indirect) on corrosion control and CM, and the latter involves about 0.05% of general corrosion cost. There is no strong division of CM methods. They range from non-direct/non-intrusive to direct/intrusive techniques. Sometimes one method (for instance, pH measurement) may be intrusive (on-line pH meter), or non-intrusive (if pH is measured for sample obtained through an existing valve). CM techniques used at the refinery units are divided on direct (weight loss - coupons and electrical resistance probes; corrosion current - linear polarization probes; remaining wall thickness - ultrasonic or eddy-current technique), and indirect (radiography, electrochemical noise measurements, chemical analytical methods, microbiological analysis of environment/deposits, heat transfer resistance method). Advantages and disadvantages of all these methods are analysed. There is no "ideal" CM method, but many of them help to detect upsets in technological processes, and to optimize the injection of chemicals (demulsifiers, neutralizers, corrosion inhibitors, biocides, scale inhibitors, oxygen scavengers). Examples of use of CM methods at the oil refinery units (atmospheric and vacuum distillation columns, cooling water systems) are given and analysed.