Influence of frequency of alternating current on corrosion of steel in seawater

Abstract

This work is a continuation of our former investigations in the field of corrosion of steel by alternating currents. In‐vestigations of corrosion of construction ship steels by alternating currents in seawater have been made. Investigations were performed within the range of alternating current densities from 20 up to 1500 mA/dm2 at frequencies from 18 up to 20000 Hz. Investigations have shown that the corrosion rate increases with the increase of current density at constant frequency. Besides, it has been established that at constant current density the corrosion rate decreases with the frequency increase up to 2000 Hz, and with the further increase of frequency up to 20000 Hz the rate of corrosion is increased. The material effect of corrosion by alternating currents in our investigations amount to 4.35–17.57% of the corrosion by equivalent densities of direct current.

A review on stray current-induced steel corrosion in infrastructure

“…It was discovered that, with increasing frequency from 5 to 500 Hz (with the same AV of 1000 mV), there was a sharp drop in the corrosion rate from about 7.5 to about 0.8 g/cm 2 /year. Overall and based on reported studies, it can be concluded that stray AC-induced steel corrosion increases with the increase of current density at constant frequency but decreases at a constant current of increasing frequency (Jones, 1978;Radeka et al, 1980;Pagano & Lalvani, 1994;Song et al, 2002;Kim et al, 2004;Fu & Cheng, 2010;Carmen et al, 2011;Zhu et al, 2014a-c). These studies also indicated that the AC corrosion of steel was only a fraction of that, which is otherwise induced by an equivalent level of DC.…”

“…Consequently, the stray current arising from these electrified traction systems may be stray DC or stray AC, where both can induce the corrosion of nearby metal structures. It should be noted that although the effects of AC stray current are more complex in the sense of more characteristic parameters, AC interference is known to be much less dangerous than DC (Radeka et al, 1980). Unlike industrial platforms that produce stray currents with a relatively stable intensity in time, the stray currents produced by electrical tractions are fluctuating in both intensity and duration (Faugt, 2006;Lingvay et al, 2008).…”

“…Corrosion caused by stray AC was first reported back in the early 1900s (Jones, 1978;Radeka et al, 1980;Pagano & Lalvani, 1994;Song et al, 2002;Kim et al, 2004Kim et al, , 2006Fu & Cheng, 2010;Büchler, 2012;Chen et al, 2013;Jiang et al, 2014;Wang et al, 2014;Zhu et al, 2014a-d). It is found that stray AC-induced corrosion is much more moderate than stray DC: in the experiments conducted by Radeka et al (1980) on ship construction steel, AC-induced corrosion damage is at the level of 4.35% to 17.57% of the equivalent densities; other researchers estimated that for metals, such as steel, lead, and copper, AC causes less than 1% of the damage caused by an equivalent DC current (Revie, 2008;Kolar & Hrbac, 2014). In practice, it is not easy to predict stray AC-induced corrosion rate by considering parameters such as alternating induced voltage.…”

“…Corrosion induced by AC currents was reported to be more detrimental at the lower AC current frequency (Radeka et al, 1980). A set of experiments was conducted by Pagano and Lalvani (1994) at various frequencies (5-500 Hz).…”

Effect of AC interference on the corrosion behavior of cathodically protected mild steel in an artificial soil solution. Part I: Investigation on formed corrosion product layer

“…[6,11,12] Büchler et al [13] suggested a corrosion mechanism based on alternating oxidation and reduction of the corrosion product layer. Previous works determined the critical parameters for AC-induced corrosion to be AC current, AC frequency, [14,15] and magnitude of the CP currents. [16] The dedicated critical parameter limits were merged into practical guidelines, such as the CeoCor [17] or NACE report.…”