An electrochemical and microstructural assessment of erosion-corrosion of austenitic cast iron for marine applications

In this paper the corrosion and erosion-corrosion characteristics of an austenitic cast iron (BS 3468 S2W) are examined under an impinging flow free from solid particles. Under static and erosioncorrosion conditions the corrosion process is controlled by activation effects and conforms to Tafel kinetics. The corrosion rate is increased under impingement conditions compared with under static conditions but the trend is complex. Although corrosion plays a part in the degradation of BS 3468 S2Wunder an impinging jet, it is clear that there is a significant role played by mechanical processes and the effect that corrosion has on the mechanical erosion processes. The pure electrochemical corrosion component of thematerial loss is reduced as a percentage of the overall weight loss on increasing the impinging jet velocity. Corrosion has been seen to initiate at the boundary between the nodules of graphite and the surrounding Fe-rich matrix and hence a physical interpretation of the effect of corrosion on erosion is identified. © WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2002.