AC Corrosion Tests of Carbon Steel, AlZnIn Anodes and 25Cr Duplex for Subsea Applications

This paper presents results from AC corrosion tests on 25Cr duplex and cathodically protected carbon steel. The results show that the corrosion rate is independent of transfer current density (0-200 A/m2) and power frequency (50-200 Hz) on cathodically protected carbon steel. On the anodes (AlZnIn), the corrosion rate increases as a function of transfer current density (0-80 A/m2). However, the correlation is less prominent at higher frequencies (100-200 Hz). For the freely corroding super duplex, the correlation is similar to that on the anodes for the highest current density (1000 A/m2). For the lowest current densities (100 A/m2), the corrosion rate was independent of power frequency. Safe levels for AC induced transfer current densities are proposed at power frequencies of 50, 100 and 200 Hz. KEY WORDS: Alternating Current Corrosion; Laboratory Tests; Carbon Steel; AlZnIn Anodes; 25Cr Duplex; Current Transfer Density.AC Corrosion Tests of Carbon Steel, AlZnIn Anodes and 25Cr Duplex for Subsea ApplicationsacceptedVersio