Harmonic analysis of carbon dioxide corrosion

Harmonic analysis (HA) has been trialed as a method for the monitoring of carbon dioxide corrosion of mild steel under a variety of conditions, i.e., in the presence and absence of hydrocarbons along with corrosion inhibitors. It has been found that it is necessary to include the third harmonic current in order to obtain reliable corrosion rates by HA. A systematic error of approximately 100% was evident in a comparison of 2500 HA corrosion rates against comparable data obtained by using linear polarisation (LP) in conjunction with assumed Tafel slopes. Conversely, a correlation of recalculated LP data by using the HA determined Tafel slopes yielded comparable corrosion rates by HA and LP. This outcome suggests that HA is capable of providing a higher degree of accuracy in studies of carbon dioxide corrosion, as compared to LP, due to the former technique's ability to determine simultaneously the Tafel slopes and corrosion rates.