I have seen bulk and surface erosion terms only in case of polymers till now.
please tell me if it is possible for metals or other materials as well and how?
Dear Dr. Singh:
The phenomenon of erosion occours at metals also, more at alloy with low density. In fact, seems more correct the term erosion-corrosion and can be taked into consideration a phenomenon mechanically actived. In almost all cases, the erosion-corrosion is correlated with a fluid in high speed or its equivalent a metal in high speed moving across a fluid. This last approach can be more current to the understanding of the phenomenon, that involve a zone of high compression level with short compression stroke and subsequent fast descompression, the sufficient to creation of the phenomenon of cavitation (this phenomenon is common at ultrasound traveling in a fluid). Then, there is increadible pressures actuating on the surface of metal, I believe that phenomenon starting to surface and in a continuous way reach the bulk with catastrophic results. In the duct case is necessary slow-dow the fluid velocity , while in helix is necessary slow-dow the rotor velocity.
kind regards
Marcos Nobre
Erosion or corrosion always starts from the surface of a bulk metal; whether it remains there or progresses into the inside of the bulk depends on whether material (oxide) is removed from the surface by flaking or shedding so that the surface can then progressively move forward into the bulk (e.g. iron and many alloys) or whether the oxide formed is stable and dense and thereby prevents further penetration by oxygen into the inside (e.g. alumina on aluminium).
In metals there is dezincification of brass, intergranular corrosion, corrosion of selective phases and internal oxidation that are the closest things I can think of to bulk erosion of polymers. Also, there is decarburization, chromium depletion, and vaporization of constituents during high temperature processing. There are many examples of surface phenomenon, such as corrosion as already mentioned and abrasive erosion.
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