Erosion–corrosion can cause an accelerated or increased rate of attack on a metal by the relative movement of a corrosive liquid. This type of attack is recognized by the appearance of waves, gullies, rounded holes, valleys and grooves. Another characteristic morphology of this type of combined attack is the scalloped appearance due to the formation of overlapping horseshoe-shaped depressions.
The lower hardness of tantalum compared with that of the stainless steels, makes this metal particularly susceptible to failure by impinging particles. Additions of tungsten, such as in Ta–2.5W, increase hardness with respect to pure tantalum, but even in this case the combined effect of a corrosive media and abrasive particles can produce in-service abrasion and erosion–corrosion failures, as can be seen in the macrographs (Fig. 4) of a Ta–2.5W reactor wall, from the same plant as the above described AISI 304L pipe.